java判断文本文件编码格式

上篇文章需要读取当前java或者配置文件的编码格式，这里主要支持UTF-8、GBK、UTF-16、Unicode等

1/**
2	 * 判断文件的编码格式
3	 * @param fileName :file
4	 * @return 文件编码格式
5	 * @throws Exception
6	 */
7	public static String codeString(File fileName) throws Exception{
8		BufferedInputStream bin = new BufferedInputStream(
9		new FileInputStream(fileName));
10		int p = (bin.read() << 8) + bin.read();
11		String code = null;
12		
13		switch (p) {
14			case 0xefbb:
15				code = "UTF-8";
16				break;
17			case 0xfffe:
18				code = "Unicode";
19				break;
20			case 0xfeff:
21				code = "UTF-16BE";
22				break;
23			default:
24				code = "GBK";
25		}
26		IOUtils.closeQuietly(bin);
27		return code;
28	}

上面这段代码只能判断带bom的文本，如果非bom文本，还有两种方式 1、 轮询常用的编码，知道找到匹配的，如下面一段测试代码

1/*
2 *  Copyright 2010 Georgios Migdos <cyberpython@gmail.com>.
3 * 
4 *  Licensed under the Apache License, Version 2.0 (the "License");
5 *  you may not use this file except in compliance with the License.
6 *  You may obtain a copy of the License at
7 * 
8 *       http://www.apache.org/licenses/LICENSE-2.0
9 * 
10 *  Unless required by applicable law or agreed to in writing, software
11 *  distributed under the License is distributed on an "AS IS" BASIS,
12 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 *  See the License for the specific language governing permissions and
14 *  limitations under the License.
15 *  under the License.
16 */
17
18import java.io.BufferedInputStream;
19import java.io.File;
20import java.io.FileInputStream;
21import java.io.FileNotFoundException;
22import java.io.IOException;
23import java.io.InputStreamReader;
24import java.nio.ByteBuffer;
25import java.nio.charset.CharacterCodingException;
26import java.nio.charset.Charset;
27import java.nio.charset.CharsetDecoder;
28
29/**
30 *
31 * @author Georgios Migdos <cyberpython@gmail.com>
32 */
33public class CharsetDetector {
34
35    public Charset detectCharset(File f, String[] charsets) {
36
37        Charset charset = null;
38
39        for (String charsetName : charsets) {
40            charset = detectCharset(f, Charset.forName(charsetName));
41            if (charset != null) {
42                break;
43            }
44        }
45
46        return charset;
47    }
48
49    private Charset detectCharset(File f, Charset charset) {
50        try {
51            BufferedInputStream input = new BufferedInputStream(new FileInputStream(f));
52
53            CharsetDecoder decoder = charset.newDecoder();
54            decoder.reset();
55
56            byte[] buffer = new byte[512];
57            boolean identified = false;
58            while ((input.read(buffer) != -1) && (!identified)) {
59                identified = identify(buffer, decoder);
60            }
61
62            input.close();
63
64            if (identified) {
65                return charset;
66            } else {
67                return null;
68            }
69
70        } catch (Exception e) {
71            return null;
72        }
73    }
74
75    private boolean identify(byte[] bytes, CharsetDecoder decoder) {
76        try {
77            decoder.decode(ByteBuffer.wrap(bytes));
78        } catch (CharacterCodingException e) {
79            return false;
80        }
81        return true;
82    }
83
84    public static void main(String[] args) {
85        File f = new File("example.txt");
86
87        String[] charsetsToBeTested = {"UTF-8", "windows-1253", "ISO-8859-7"};
88
89        CharsetDetector cd = new CharsetDetector();
90        Charset charset = cd.detectCharset(f, charsetsToBeTested);
91
92        if (charset != null) {
93            try {
94                InputStreamReader reader = new InputStreamReader(new FileInputStream(f), charset);
95                int c = 0;
96                while ((c = reader.read()) != -1) {
97                    System.out.print((char)c);
98                }
99                reader.close();
100            } catch (FileNotFoundException fnfe) {
101                fnfe.printStackTrace();
102            }catch(IOException ioe){
103                ioe.printStackTrace();
104            }
105
106        }else{
107            System.out.println("Unrecognized charset.");
108        }
109    }
110}
111    

2、 使用谷歌依赖库来进行判断 https://code.google.com/archive/p/juniversalchardet/