<div class="htmledit\_views" id="content\_views"> <p>https://blog.csdn.net/mcryeasy/article/details/52344729<br></p><p>待优化整理 总结</p><p></p><h1 style="padding:0px;font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><a name="t0"></a>Class类简介</h1><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> 在java世界里，一切皆对象。从某种意义上来说，java有两种对象：实例对象和Class对象。每个类的运行时的<span style="font-weight:700;">类型信息</span>就是用Class对象表示的。它包含了与类有关的信息。其实我们的实例对象就通过Class对象来创建的。Java使用Class对象执行其RTTI（运行时类型识别，Run-Time Type Identification），多态是基于RTTI实现的。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> 每一个类都有一个Class对象，每当编译一个新类就产生一个Class对象，基本类型 (boolean, byte, char, short, int, long, float, and double)有Class对象，数组有Class对象，就连关键字void也有Class对象（void.class）。Class对象对应着java.lang.Class类，如果说类是对象抽象和集合的话，那么Class类就是对类的抽象和集合。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> Class类没有公共的构造方法，Class对象是在类加载的时候由<span style="font-weight:700;">Java虚拟机</span>以及通过调用类加载器中的 defineClass 方法自动构造的，因此不能显式地声明一个Class对象。一个类被加载到内存并供我们使用需要经历如下三个阶段：</p><ol style="list-style:none;color:rgb(51,51,51);font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;font-size:14px;background-color:rgb(255,255,255);"><li style="padding:0px;margin-right:0px;margin-bottom:0px;"><p><span style="font-weight:700;">加载</span>，这是由类加载器（ClassLoader）执行的。通过一个类的全限定名来获取其定义的二进制字节流（Class字节码），将这个字节流所代表的静态存储结构转化为方法去的运行时数据接口，根据字节码在java堆中生成一个代表这个类的java.lang.Class对象。</p></li><li style="padding:0px;margin-right:0px;margin-bottom:0px;"><p><span style="font-weight:700;">链接</span>。在链接阶段将验证Class文件中的字节流包含的信息是否符合当前虚拟机的要求，为静态域分配存储空间并设置类变量的初始值（默认的零值），并且如果必需的话，将常量池中的符号引用转化为直接引用。</p></li><li style="padding:0px;margin-right:0px;margin-bottom:0px;"><p><span style="font-weight:700;">初始化</span>。到了此阶段，才真正开始执行类中定义的java程序代码。用于执行该类的静态初始器和静态初始块，如果该类有父类的话，则优先对其父类进行初始化。</p></li></ol><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> <br> <span style="font-weight:700;">所有的类都是在对其第一次使用时，动态加载到JVM中的（懒加载）。</span>当程序创建第一个对类的静态成员的引用时，就会加载这个类。使用new创建类对象的时候也会被当作对类的静态成员的引用。<span style="font-weight:700;">因此java程序程序在它开始运行之前并非被完全加载，其各个类都是在必需时才加载的。</span>这一点与许多传统语言都不同。动态加载使能的行为，在诸如C++这样的静态加载语言中是很难或者根本不可能复制的。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> 在类加载阶段，类加载器首先检查这个类的Class对象是否已经被加载。如果尚未加载，默认的类加载器就会根据类的全限定名查找.class文件。在这个类的字节码被加载时，它们会接受验证，以确保其没有被破坏，并且不包含不良java代码。一旦某个类的Class对象被载入内存，我们就可以它来创建这个类的所有对象。</p><hr style="color:rgb(51,51,51);font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;font-size:14px;background-color:rgb(255,255,255);"><h1 style="padding:0px;font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><a name="t1"></a><a></a>如何获得Class对象</h1><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">有三种获得Class对象的方式：</p><ol style="list-style:none;color:rgb(51,51,51);font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;font-size:14px;background-color:rgb(255,255,255);"><li style="padding:0px;margin-right:0px;margin-bottom:0px;">Class.forName(“类的全限定名”)</li><li style="padding:0px;margin-right:0px;margin-bottom:0px;">实例对象.getClass()</li><li style="padding:0px;margin-right:0px;margin-bottom:0px;">类名.class （类字面常量）</li></ol><h2 style="padding:0px;font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><a name="t2"></a><a></a>Class.forName 和getClass()</h2><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">我们先看看如下的例子：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs cs"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">package</span> com.cry;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword">class</span></span> <span class="hljs-title"><span class="hljs-title">Dog</span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Loading Dog"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword">class</span></span> <span class="hljs-title"><span class="hljs-title">Cat</span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Loading Cat"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">class</span></span></span> <span class="hljs-title"><span class="hljs-title"><span class="hljs-title">Test</span></span></span> {</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">public</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">static</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">void</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-title"><span class="hljs-function"><span class="hljs-title"><span class="hljs-function"><span class="hljs-title">main</span></span></span></span></span><span class="hljs-function"><span class="hljs-function">(</span><span class="hljs-params"><span class="hljs-function"><span class="hljs-params">String\[\] args</span></span></span><span class="hljs-function">)</span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"inside main"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">new</span></span></span> Dog();</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"after creating Dog"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">try</span></span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Class cat=Class.forName(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"com.cry.Cat"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> } <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">catch</span></span></span> (ClassNotFoundException e) {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Couldn't find Cat"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="22"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"finish main"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="23"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="24"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="25"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">/\* Output:</span></span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="26"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> inside main</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="27"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> Loading Dog</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="28"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> after creating Dog</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="29"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> Loading Cat</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="30"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> finish main</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="31"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> \*/</span></span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> 上面的Dog、Cat类中都有一个静态语句块，该语句块在类第一次被加载时候被执行。这时会有相应的信息打印出来，告诉我们这个类什么时候被加载了。从输出中可以看到，Class对象仅在需要的时候才被加载，static初始化是在类加载时进行的。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> Class.forName方法是Class类的一个静态成员。forName在执行的过程中发现如果类Dog还没有被加载，那么JVM就会调用类加载器去加载Dog类，并返回加载后的Class对象。Class对象和其他对象一样，我们可以获取并操作它的引用。在类加载的过程中，Dog类的静态语句块会被执行。如果Class .forName找不到你要加载的类，它会抛出ClassNotFoundException异常。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> Class.forName的好处就在于，不需要为了获得Class引用而持有该类型的对象，只要通过全限定名就可以返回该类型的一个Class引用。如果你已经有了该类型的对象，那么我们就可以通过调用getClass()方法来获取Class引用了，这个方法属于根类Object的一部分，它返回的是表示该对象的实际类型的Class引用：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs cs"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">package</span> com.cry;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword">class</span></span> <span class="hljs-title"><span class="hljs-title">Dog</span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Loading Dog"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">class</span></span></span> <span class="hljs-title"><span class="hljs-title"><span class="hljs-title">Test</span></span></span> {</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">public</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">static</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">void</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-title"><span class="hljs-function"><span class="hljs-title"><span class="hljs-function"><span class="hljs-title">main</span></span></span></span></span><span class="hljs-function"><span class="hljs-function">(</span><span class="hljs-params"><span class="hljs-function"><span class="hljs-params">String\[\] args</span></span></span><span class="hljs-function">) </span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"inside main"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Dog d = <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">new</span></span></span> Dog();</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"after creating Dog"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Class c = d.getClass();</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"finish main"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">/\* Output:</span></span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> inside main</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> Loading Dog</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> after creating Dog</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> finish main</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> \*/</span></span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">利用new操作符创建对象后，类已经装载到内存中了，所以执行getClass()方法的时候，就不会再去执行类加载的操作了，而是直接从java堆中返回该类型的Class引用。</p><h2 style="padding:0px;font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><a name="t3"></a><a></a>类字面常量</h2><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> java还提供了另一种方法来生成对Class对象的引用。即使用类字面常量，就像这样：Cat.class，这样做不仅更简单，而且更安全，因为它在编译时就会受到检查(因此不需要置于try语句块中)。并且根除了对forName()方法的调用，所有也更高效。类字面量不仅可以应用于普通的类，也可以应用于接口、数组及基本数据类型。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">注意：基本数据类型的Class对象和包装类的Class对象是不一样的：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs vbscript"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword">Class</span></span> c1 = Integer.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword">Class</span></span> c2 = <span class="hljs-keyword"><span class="hljs-built\_in"><span class="hljs-built\_in">int</span></span></span>.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">System.out.println(c1);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">System.out.println(c2);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">System.out.println(c1 == c2);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment">/\* Output</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">class</span> java.lang.Integer</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-built\_in">int</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-literal">false</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">\*/</div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">但是在包装类中有个一个字段TYPE，TYPE字段是一个引用，指向对应的基本数据类型的Class对象，如下所示，左右两边相互等价： <br><img src="https://img-blog.csdn.net/20160828123308282" alt="这里写图片描述" title="" style="margin-top:24px;margin-bottom:24px;"> <br> <br> <span style="font-weight:700;">用.class来创建对Class对象的引用时，不会自动地初始化该Class对象</span>（这点和Class.forName方法不同）。类对象的初始化阶段被延迟到了对静态方法或者非常数静态域首次引用时才执行：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs swift"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">package</span> com.cry;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Dog</span></span></span><span class="hljs-class"> </span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">final</span></span></span> <span class="hljs-type"><span class="hljs-type">String</span></span> s1 = <span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Dog\_s1"</span></span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-type"><span class="hljs-type">String</span></span> s2 = <span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Dog\_s2"</span></span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Loading Dog"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Cat</span></span></span><span class="hljs-class"> </span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-type"><span class="hljs-type">String</span></span> s1 = <span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Cat\_s1"</span></span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Loading Cat"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Test</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span>{</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-type"><span class="hljs-type">String</span></span>\[\] args) <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">throws</span></span></span> <span class="hljs-type"><span class="hljs-type">ClassNotFoundException</span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"----Star Dog----"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">Class</span></span> dog = <span class="hljs-type"><span class="hljs-type">Dog</span></span>.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"------"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-type"><span class="hljs-type">Dog</span></span>.s1);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"------"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="22"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-type"><span class="hljs-type">Dog</span></span>.s2);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="23"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"---start Cat---"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="24"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">Class</span></span> cat = <span class="hljs-type"><span class="hljs-type">Class</span></span>.forName(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"com.cry.Cat"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="25"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"-------"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="26"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-type"><span class="hljs-type">Cat</span></span>.s1);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="27"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-type"><span class="hljs-type">System</span></span>.out.<span class="hljs-built\_in"><span class="hljs-built\_in">println</span></span>(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"finish main"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="28"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="29"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="30"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">/\* Output:</span></span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="31"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">----Star Dog----</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="32"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">------</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="33"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">Dog\_s1</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="34"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">------</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="35"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">Loading Dog</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="36"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">Dog\_s2</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="37"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">---start Cat---</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="38"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">Loading Cat</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="39"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">-------</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="40"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">Cat\_s1</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="41"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">finish main</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="42"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> \*/</span></span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> 从上面我们可以看到，如果仅使用.class语法来获得对类的Class引用是不会引发初始化的。但是如果使用Class.forName来产生引用，就会立即进行了初始化，就像Cat所看到的。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> <span style="font-weight:700;">如果一个字段被static final修饰，我们称为”编译时常量“，就像Dog的s1字段那样，那么在调用这个字段的时候是不会对Dog类进行初始化的。</span>因为被static和final修饰的字段，在编译期就把结果放入了常量池中了。但是，如果只是将一个域设置为static 或final的，还不足以确保这种行为，就如调用Dog的s2字段后，会强制Dog进行类的初始化，因为s2字段不是一个编译时常量。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">通过javap -c -v对Dog的字节码进行反汇编：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs cpp"><ol class="hljs-ln" style="width:959px"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword">final</span> java.lang.String s1;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> flags: ACC\_STATIC, ACC\_FINAL</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> ConstantValue: String Dog\_s1</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> java.lang.String s2;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> flags: ACC\_STATIC</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> com.cry.Dog();</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> flags:</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Code:</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-built\_in"><span class="hljs-built\_in">stack</span></span>=<span class="hljs-number"><span class="hljs-number"><span class="hljs-number">1</span></span></span>, locals=<span class="hljs-number"><span class="hljs-number"><span class="hljs-number">1</span></span></span>, args\_size=<span class="hljs-number"><span class="hljs-number"><span class="hljs-number">1</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-number"><span class="hljs-number"><span class="hljs-number">0</span></span></span>: aload\_0</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-number"><span class="hljs-number"><span class="hljs-number">1</span></span></span>: invokespecial #<span class="hljs-number"><span class="hljs-number"><span class="hljs-number">1</span></span></span> <span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">// Method java/lang/Object."<init>":()V</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">4</span></span></span><span class="hljs-comment">: </span><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-comment">return</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> LineNumberTable:</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> line </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">3</span></span></span><span class="hljs-comment">: </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">0</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> LocalVariableTable:</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> Start Length Slot Name Signature</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">0</span></span></span><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">5</span></span></span><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">0</span></span></span><span class="hljs-comment"> </span><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-comment">this</span></span></span><span class="hljs-comment"> Lcom/cry/Dog;</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-comment">static</span></span></span><span class="hljs-comment"> {};</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> flags: ACC\_STATIC</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> Code:</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="22"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-built\_in"><span class="hljs-comment">stack</span></span><span class="hljs-comment">=</span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">2</span></span></span><span class="hljs-comment">, locals=</span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">0</span></span></span><span class="hljs-comment">, args\_size=</span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">0</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="23"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">0</span></span></span><span class="hljs-comment">: ldc #</span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">2</span></span></span><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">// String Dog\_s2</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="24"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">2</span></span></span><span class="hljs-comment">: putstatic #</span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">3</span></span></span><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">// Field s2:Ljava/lang/String;</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="25"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">5</span></span></span><span class="hljs-comment">: getstatic #</span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">4</span></span></span><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">// Field java/lang/System.out:Ljava/io/PrintStream;</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="26"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">8</span></span></span><span class="hljs-comment">: ldc #</span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">5</span></span></span><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">// String Loading Dog</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="27"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">10</span></span></span><span class="hljs-comment">: invokevirtual #</span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">6</span></span></span><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">// Method java/io/PrintStream.println:(Ljava/lang/String;)V</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="28"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">13</span></span></span><span class="hljs-comment">: </span><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-comment">return</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="29"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> LineNumberTable:</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="30"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> line </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">6</span></span></span><span class="hljs-comment">: </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">0</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="31"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> line </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">9</span></span></span><span class="hljs-comment">: </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">5</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="32"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> line </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">10</span></span></span><span class="hljs-comment">: </span><span class="hljs-number"><span class="hljs-number"><span class="hljs-comment">13</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="33"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment">}</span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> 从上面可以看出s1在编译后被ConstantValue属性修饰 ConstantValue: String Dog\_s1，表示即同时被final和static修饰。而s2并没有被ConstantValue修饰，因为它不是一个编译时常量。在static{}中表示类的初始化操作，在操作中我们看到只有s2字段进行了赋值，而却没有s1的踪影，因此调用s1字段是不会触发类的初始化的。</p><h2 style="padding:0px;font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><a name="t4"></a><a></a>小结</h2><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> 一旦类被加载了到了内存中，那么不论通过哪种方式获得该类的Class对象，它们返回的都是指向同一个java堆地址上的Class引用。jvm不会创建两个相同类型的Class对象：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs cs"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">package</span> com.cry;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword">class</span></span> <span class="hljs-title"><span class="hljs-title">Cat</span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"Loading Cat"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">class</span></span></span> <span class="hljs-title"><span class="hljs-title"><span class="hljs-title">Test</span></span></span> {</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">public</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">static</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">void</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-title"><span class="hljs-function"><span class="hljs-title"><span class="hljs-function"><span class="hljs-title">main</span></span></span></span></span><span class="hljs-function"><span class="hljs-function">(</span><span class="hljs-params"><span class="hljs-function"><span class="hljs-params">String\[\] args</span></span></span><span class="hljs-function">) </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-function">throws</span></span></span><span class="hljs-function"><span class="hljs-function"> ClassNotFoundException </span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"inside main"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Class c1 = Cat.class;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Class c2= Class.forName(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"com.cry.Cat"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Class c3=<span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">new</span></span></span> Cat().getClass();</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Class c4 =<span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">new</span></span></span> Cat().getClass();</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(c1==c2);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(c2==c3);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> System.<span class="hljs-keyword"><span class="hljs-keyword">out</span></span>.println(<span class="hljs-string"><span class="hljs-string"><span class="hljs-string">"finish main"</span></span></span>);</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">/\* Output:</span></span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">inside main</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">-------</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="22"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">Loading Cat</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="23"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">true</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="24"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">true</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="25"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment">finish main</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="26"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> \*/</span></span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">从上面我们可以看出执行不同获取Class引用的方法，返回的其实都是同一个Class对象。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> <span style="font-weight:700;">其实对于任意一个Class对象，都需要由它的类加载器和这个类本身一同确定其在就Java虚拟机中的唯一性，也就是说，即使两个Class对象来源于同一个Class文件，只要加载它们的类加载器不同，那这两个Class对象就必定不相等。</span>这里的“相等”包括了代表类的Class对象的equals（）、isAssignableFrom（）、isInstance（）等方法的返回结果，也包括了使用instanceof关键字对对象所属关系的判定结果。所以在java虚拟机中使用<span style="font-weight:700;">双亲委派模型</span>来组织类加载器之间的关系，来保证Class对象的唯一性。</p><hr style="color:rgb(51,51,51);font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;font-size:14px;background-color:rgb(255,255,255);"><h1 style="padding:0px;font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><a name="t5"></a><a></a>泛型Class引用</h1><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> Class引用表示的就是它所指向的对象的确切类型，而该对象便是Class类的一个对象。在JavaSE5中，允许你对Class引用所指向的Class对象的类型进行限定，也就是说你可以对Class对象使用泛型语法。通过泛型语法，可以让编译器强制指向额外的类型检查：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs kotlin groovy"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">final</span></span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Class</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"><</span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-type"><span class="hljs-class"><span class="hljs-title">T</span></span></span></span></span><span class="hljs-class"><span class="hljs-class">> </span></span><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-keyword">implements</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">java</span></span></span></span></span><span class="hljs-class"><span class="hljs-class">.</span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">io</span></span></span></span></span><span class="hljs-class"><span class="hljs-class">.</span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Serializable</span></span></span></span></span><span class="hljs-class"><span class="hljs-class">,</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-type"><span class="hljs-class"><span class="hljs-title">GenericDeclaration</span></span></span></span></span><span class="hljs-class"><span class="hljs-class">,</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-type"><span class="hljs-class"><span class="hljs-title">Type</span></span></span></span></span><span class="hljs-class"><span class="hljs-class">,</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-type"><span class="hljs-class"><span class="hljs-title">AnnotatedElement</span></span></span></span></span><span class="hljs-class"><span class="hljs-type"><span class="hljs-class"> {</span></span></span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs delphi"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword">Class</span></span><Integer> c1 = <span class="hljs-keyword">int</span>.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> c1=Integer.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//c1=Double.class; 编译报错</span></span></span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">虽然int.class和Integer.class指向的不是同一个Class对象引用，但是它们基本类型和包装类的关系，int可以自动包装为Integer，所以编译器可以编译通过。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">泛型中的类型可以持有其子类的引用吗？不行：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs delphi"><span class="hljs-keyword"><span class="hljs-keyword">Class</span></span><Number> c1 = Integer.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>; <span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//编译报错</span></span></span></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">虽然Integer继承自Number，但是编译器无法编译通过。</p><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">为了使用泛化的Class引用放松限制，我们还可以使用通配符，它是Java泛型的一部分。通配符的符合是”?“，表示“任何事物“：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs vbscript"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword">Class</span></span><?> c1 = <span class="hljs-keyword"><span class="hljs-built\_in"><span class="hljs-built\_in">int</span></span></span>.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> c1= <span class="hljs-keyword">double</span>.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">Class</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs delphi"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword">Class</span></span><? extends Number> c1 = Integer.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> c1 = Number.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> c1 = Double.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">// c1=String.class; 报错，不属于Number类和其子类</span></span></span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">通配符?不仅可以与extend结合，而且还可以与super关键字相结合，表示被限定为某种类型，或该类型的任何父类型：</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs vbnet"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword">Class</span></span><? <span class="hljs-keyword">super</span> <span class="hljs-built\_in"><span class="hljs-built\_in">Integer</span></span>> c1 = <span class="hljs-built\_in"><span class="hljs-built\_in">Integer</span></span>.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> c1 = Number.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> c1 = <span class="hljs-built\_in"><span class="hljs-built\_in">Object</span></span>.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> c1=<span class="hljs-built\_in"><span class="hljs-built\_in">Integer</span></span>.<span class="hljs-keyword"><span class="hljs-keyword">class</span></span>.getSuperclass();</div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">向Class引用添加泛型语法的原因仅仅是为了提供编译期类型检查。</p><hr style="color:rgb(51,51,51);font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;font-size:14px;background-color:rgb(255,255,255);"><h1 style="padding:0px;font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><a name="t6"></a><a></a>Class类的方法</h1><div class="table-box"><table style="border-spacing:0px;width:851.667px;text-align:center;color:rgb(51,51,51);font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;font-size:14px;background-color:rgb(255,255,255);"><thead><tr><th align="center" style="margin:0px;vertical-align:middle;">方法名</th><th style="margin:0px;vertical-align:middle;">说明</th></tr></thead><tbody><tr><td align="center" style="margin:0px;vertical-align:middle;">forName()</td><td style="margin:0px;vertical-align:middle;">(1)获取Class对象的一个引用，但引用的类还没有加载(该类的第一个对象没有生成)就加载了这个类。<br>(2)为了产生Class引用，forName()立即就进行了初始化。</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">Object-getClass()</td><td style="margin:0px;vertical-align:middle;">获取Class对象的一个引用，返回表示该对象的实际类型的Class引用。</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">getName()</td><td style="margin:0px;vertical-align:middle;">取全限定的类名(包括包名)，即类的完整名字。</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">getSimpleName()</td><td style="margin:0px;vertical-align:middle;">获取类名(不包括包名)</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">getCanonicalName()</td><td style="margin:0px;vertical-align:middle;">获取全限定的类名(包括包名)</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">isInterface()</td><td style="margin:0px;vertical-align:middle;">判断Class对象是否是表示一个接口</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">getInterfaces()</td><td style="margin:0px;vertical-align:middle;">返回Class对象数组，表示Class对象所引用的类所实现的所有接口。</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">getSupercalss()</td><td style="margin:0px;vertical-align:middle;">返回Class对象，表示Class对象所引用的类所继承的直接基类。应用该方法可在运行时发现一个对象完整的继承结构。</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">newInstance()</td><td style="margin:0px;vertical-align:middle;">返回一个Oject对象，是实现“虚拟构造器”的一种途径。<span style="font-weight:700;">使用该方法创建的类，必须带有无参的构造器</span>。</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">getFields()</td><td style="margin:0px;vertical-align:middle;">获得某个类的所有的公共（public）的字段，包括继承自父类的所有公共字段。 类似的还有getMethods和getConstructors。</td></tr><tr><td align="center" style="margin:0px;vertical-align:middle;">getDeclaredFields</td><td style="margin:0px;vertical-align:middle;">获得某个类的自己声明的字段，即包括public、private和proteced，默认但是不包括父类声明的任何字段。类似的还有getDeclaredMethods和getDeclaredConstructors。</td></tr></tbody></table></div><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"> </p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs java"><ol class="hljs-ln" style="width:900px"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">package</span></span></span> com.cry;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">import</span></span></span> java.lang.reflect.Field;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">interface</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">I1</span></span></span><span class="hljs-class"> </span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">interface</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">I2</span></span></span><span class="hljs-class"> </span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Cell</span></span></span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mCellPublic;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Animal</span></span></span><span class="hljs-class"> </span><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">extends</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Cell</span></span></span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">private</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mAnimalPrivate;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">protected</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mAnimalProtected;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mAnimalDefault;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mAnimalPublic;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">private</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> sAnimalPrivate;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">protected</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> sAnimalProtected;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> sAnimalDefault;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> sAnimalPublic;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Dog</span></span></span><span class="hljs-class"> </span><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">extends</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Animal</span></span></span><span class="hljs-class"> </span><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">implements</span></span></span><span class="hljs-class"> </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">I1</span></span></span><span class="hljs-class">, </span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">I2</span></span></span><span class="hljs-class"> </span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">private</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mDogPrivate;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="22"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mDogPublic;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="23"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">protected</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mDogProtected;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="24"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">private</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> mDogDefault;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="25"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">private</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> sDogPrivate;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="26"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">protected</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> sDogProtected;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="27"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> sDogDefault;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="28"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">int</span></span></span> sDogPublic;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="29"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line">}</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="30"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Test</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span>{</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="31"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">public</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">static</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">void</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> </span></span><span class="hljs-title"><span class="hljs-function"><span class="hljs-title"><span class="hljs-function"><span class="hljs-title">main</span></span></span></span></span><span class="hljs-function"><span class="hljs-params"><span class="hljs-function"><span class="hljs-params">(String\[\] args)</span></span></span><span class="hljs-function"> </span></span><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">throws</span></span></span></span></span><span class="hljs-function"><span class="hljs-function"> IllegalAccessException, InstantiationException </span></span>{</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="32"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> Class<Dog> dog = Dog.class;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="33"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//类名打印</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="34"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(dog.getName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//com.cry.Dog</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="35"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(dog.getSimpleName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//Dog</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="36"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(dog.getCanonicalName());</span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//com.cry.Dog</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="37"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//接口</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="38"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(dog.isInterface()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//false</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="39"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-comment">for</span></span></span><span class="hljs-comment"> (Class iI : dog.getInterfaces()) {</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="40"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(iI);</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="41"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> }</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="42"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">/\*</span></span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="43"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> interface com.cry.I1</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="44"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> interface com.cry.I2</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="45"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> \*/</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="46"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="47"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//父类</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="48"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(dog.getSuperclass());</span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//class com.cry.Animal</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="49"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//创建对象</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="50"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> Dog d = dog.newInstance();</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="51"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//字段</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="52"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-comment">for</span></span></span><span class="hljs-comment"> (Field f : dog.getFields()) {</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="53"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(f.getName());</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="54"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> }</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="55"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">/\*</span></span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="56"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> mDogPublic</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="57"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> sDogPublic</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="58"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> mAnimalPublic</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="59"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> sAnimalPublic</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="60"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> mCellPublic //父类的父类的公共字段也打印出来了</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="61"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> \*/</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="62"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(</span><span class="hljs-string"><span class="hljs-string"><span class="hljs-comment">"---------"</span></span></span><span class="hljs-comment">);</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="63"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-comment">for</span></span></span><span class="hljs-comment"> (Field f : dog.getDeclaredFields()) {</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="64"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> System.out.println(f.getName());</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="65"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> }</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="66"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-javadoc"><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">/\*\* 只有自己类声明的字段</span></span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="67"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> mDogPrivate</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="68"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> mDogPublic</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="69"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> mDogProtected</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="70"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> mDogDefault</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="71"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> sDogPrivate</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="72"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> sDogProtected</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="73"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> sDogDefault</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="74"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> sDogPublic</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="75"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"><span class="hljs-comment"> \*/</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="76"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> }</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="77"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment">}</span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><h2 style="padding:0px;font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><a name="t7"></a><a></a>getName、getCanonicalName与getSimpleName的区别：</h2><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);"><span style="font-weight:700;">getSimpleName</span>：只获取类名 <br><span style="font-weight:700;">getName</span>：类的全限定名，jvm中Class的表示，可以用于动态加载Class对象，例如Class.forName。 <br><span style="font-weight:700;">getCanonicalName</span>：返回更容易理解的表示，主要用于输出（toString）或log打印，大多数情况下和getName一样，但是在内部类、数组等类型的表示形式就不同了。</p><pre class="prettyprint" style="font-size:14px;line-height:22px;" name="code"><code class="hljs swift"><ol class="hljs-ln"><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="1"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword">package</span> com.cry;</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="2"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">Test</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span>{</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="3"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">private</span></span></span> <span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword"><span class="hljs-class"><span class="hljs-keyword">class</span></span></span></span></span><span class="hljs-class"><span class="hljs-class"> </span></span><span class="hljs-title"><span class="hljs-class"><span class="hljs-title"><span class="hljs-class"><span class="hljs-title">inner</span></span></span></span></span>{</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="4"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> }</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="5"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">public</span></span></span> <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">static</span></span></span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-type"><span class="hljs-type">String</span></span>\[\] args) <span class="hljs-keyword"><span class="hljs-keyword"><span class="hljs-keyword">throws</span></span></span> <span class="hljs-type"><span class="hljs-type">ClassNotFoundException</span></span> {</div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="6"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//普通类</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="7"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(</span><span class="hljs-type"><span class="hljs-comment">Test</span></span><span class="hljs-comment">.</span><span class="hljs-keyword"><span class="hljs-comment">class</span></span><span class="hljs-comment">.getSimpleName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//Test</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="8"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(</span><span class="hljs-type"><span class="hljs-comment">Test</span></span><span class="hljs-comment">.</span><span class="hljs-keyword"><span class="hljs-comment">class</span></span><span class="hljs-comment">.getName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//com.cry.Test</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="9"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(</span><span class="hljs-type"><span class="hljs-comment">Test</span></span><span class="hljs-comment">.</span><span class="hljs-keyword"><span class="hljs-comment">class</span></span><span class="hljs-comment">.getCanonicalName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//com.cry.Test</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="10"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//内部类</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="11"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(inner.</span><span class="hljs-keyword"><span class="hljs-comment">class</span></span><span class="hljs-comment">.getSimpleName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//inner</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="12"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(inner.</span><span class="hljs-keyword"><span class="hljs-comment">class</span></span><span class="hljs-comment">.getName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//com.cry.Test$inner</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="13"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(inner.</span><span class="hljs-keyword"><span class="hljs-comment">class</span></span><span class="hljs-comment">.getCanonicalName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//com.cry.Test.inner</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="14"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//数组</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="15"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(args.getClass().getSimpleName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//String\[\]</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="16"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(args.getClass().getName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//\[Ljava.lang.String;</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="17"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">System</span></span><span class="hljs-comment">.out.</span><span class="hljs-built\_in"><span class="hljs-comment">println</span></span><span class="hljs-comment">(args.getClass().getCanonicalName()); </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//java.lang.String\[\]</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="18"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//我们不能用getCanonicalName去加载类对象，必须用getName</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="19"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-comment"><span class="hljs-comment"><span class="hljs-comment">//Class.forName(inner.class.getCanonicalName()); 报错</span></span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="20"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> </span><span class="hljs-type"><span class="hljs-comment">Class</span></span><span class="hljs-comment">.forName(inner.</span><span class="hljs-keyword"><span class="hljs-comment">class</span></span><span class="hljs-comment">.getName());</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="21"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment"> }</span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="22"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"><span class="hljs-comment">}</span></div></div></li></ol></code><div class="hljs-button signin" data-title="登录后复制" onclick="hljs.signin(event)"></div></pre><hr style="color:rgb(51,51,51);font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;font-size:14px;background-color:rgb(255,255,255);"><p style="font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;background-color:rgb(255,255,255);">参考： <br><a href="http://blog.csdn.net/vivianboypan/article/details/7830756?utm\_source=tuicool&utm\_medium=referral" rel="nofollow" data-token="c1254026ca2e8fa84ae0f087c1cbd78d">java中的Class对象和new关键字解析</a> <br>Thinking in Java</p><br> 原文地址：https://blog.csdn.net/dufufd/article/details/80537638 </div>
