java 编码格式判断 java 文件编码判断

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

/**
* 判断文件的编码格式
* @param fileName :file
* @return 文件编码格式
* @throws Exception
*/
public static String codeString(File fileName) throws Exception{
BufferedInputStream bin = new BufferedInputStream(
new FileInputStream(fileName));
int p = (bin.read() << 8) + bin.read();
String code = null;
switch (p) {
case 0xefbb:
code = "UTF-8";
break;
case 0xfffe:
code = "Unicode";
break;
case 0xfeff:
code = "UTF-16BE";
break;
default:
code = "GBK";
}
IOUtils.closeQuietly(bin);
return code;
}

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

/*
* Copyright 2010 Georgios Migdos .
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* under the License.
*/
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
/**
*
* @author Georgios Migdos 
*/
public class CharsetDetector {
public Charset detectCharset(File f, String[] charsets) {
Charset charset = null;
for (String charsetName : charsets) {
charset = detectCharset(f, Charset.forName(charsetName));
if (charset != null) {
break;
}
}
return charset;
}
private Charset detectCharset(File f, Charset charset) {
try {
BufferedInputStream input = new BufferedInputStream(new FileInputStream(f));
CharsetDecoder decoder = charset.newDecoder();
decoder.reset();
byte[] buffer = new byte[512];
boolean identified = false;
while ((input.read(buffer) != -1) && (!identified)) {
identified = identify(buffer, decoder);
}
input.close();
if (identified) {
return charset;
} else {
return null;
}
} catch (Exception e) {
return null;
}
}
private boolean identify(byte[] bytes, CharsetDecoder decoder) {
try {
decoder.decode(ByteBuffer.wrap(bytes));
} catch (CharacterCodingException e) {
return false;
}
return true;
}
public static void main(String[] args) {
File f = new File("example.txt");
String[] charsetsToBeTested = {"UTF-8", "windows-1253", "ISO-8859-7"};
CharsetDetector cd = new CharsetDetector();
Charset charset = cd.detectCharset(f, charsetsToBeTested);
if (charset != null) {
try {
InputStreamReader reader = new InputStreamReader(new FileInputStream(f), charset);
int c = 0;
while ((c = reader.read()) != -1) {
System.out.print((char)c);
}
reader.close();
} catch (FileNotFoundException fnfe) {
fnfe.printStackTrace();
}catch(IOException ioe){
ioe.printStackTrace();
}
}else{
System.out.println("Unrecognized charset.");
}
}
}