补充关于equals的比较方式

补充(equals比较)

Object中的equals比较的是地址

1  public boolean equals(Object obj) {
2    return (this == obj);
3}

java.lang.String类中equals的方法

equals判断相等依据

策略：如果与目标相等返回0，小于目标返回值小于0，大于目标返回值大于0

1@Native static final byte LATIN1 = 0;
2@Native static final byte UTF16  = 1;

1  /**
2 * Compares this string to the specified object.  The result is {@code
3 * true} if and only if the argument is not {@code null} and is a {@code
4 * String} object that represents the same sequence of characters as this
5 * object.
6 *
7 * <p>For finer-grained String comparison, refer to
8 * {@link java.text.Collator}.
9 *
10 * @param  anObject
11 *         The object to compare this {@code String} against
12 *
13 * @return  {@code true} if the given object represents a {@code String}
14 *          equivalent to this string, {@code false} otherwise
15 *
16 * @see  #compareTo(String)
17 * @see  #equalsIgnoreCase(String)
18 */
19public boolean equals(Object anObject) {
20    if (this == anObject) {
21        return true;
22    }
23    if (anObject instanceof String) {
24        String aString = (String)anObject;
25        if (coder() == aString.coder()) {
26            return isLatin1() ? StringLatin1.equals(value, aString.value)
27                              : StringUTF16.equals(value, aString.value);
28        }
29    }
30    return false;
31}
32
33private boolean isLatin1() {
34     return COMPACT_STRINGS && coder == LATIN1;
35}
36
37###StringLatin1.equals|
38@HotSpotIntrinsicCandidate
39    public static boolean equals(byte[] value, byte[] other) {
40        if (value.length == other.length) {
41            for (int i = 0; i < value.length; i++) {
42                if (value[i] != other[i]) {
43                    return false;
44                }
45            }
46            return true;
47        }
48        return false;
49    }
50
51###StringUTF16.equals|
52@HotSpotIntrinsicCandidate
53    public static boolean equals(byte[] value, byte[] other) {
54        if (value.length == other.length) {
55            int len = value.length >> 1;
56            for (int i = 0; i < len; i++) {
57                if (getChar(value, i) != getChar(other, i)) {
58                    return false;
59                }
60            }
61            return true;
62        }
63        return false;
64    }

注：更细粒度的equals比较，先比较地址是否相同，看其是否为空，最后看其编码值比较