Java工具箱之字符编码工具类

涉及到文件的字符编码问题一般需要知道两个内容：

1、文件本身的字符编码是什么？

2、如何将文件的字符编码集转换为另一种？

这个工具类就解决这两个问题

package com.trigl.util;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;

/**
* 字符编码工具类
* @author 白鑫
*  2016年7月26日 下午7:18:01
*/
public class EncodingUtil {

/**
* 获取指定文件的字符编码类型
* @param filePath
* @return
*/
@SuppressWarnings("resource")
public static String getFileCharset(String filePath) {
String charset = "GBK";
byte[] f3b = new byte[3];
try {
boolean check = false;
BufferedInputStream bis = new BufferedInputStream(
new FileInputStream(filePath));
bis.mark(0);
int read = bis.read(f3b, 0, 3);
if (read == -1) {
return charset;
} else if (f3b[0] == (byte) 0xFF && f3b[1] == (byte) 0xFE) {
charset = "UTF-16LE";
check = true;
} else if (f3b[0] == (byte) 0xEF && f3b[1] == (byte) 0xBB
&& f3b[2] == (byte) 0xBF) {
charset = "UTF-8";
check = true;
}
bis.reset();
if (!check) {
while ((read = bis.read()) != -1) {
if (read >= 0xF0)
break;

if (0x80 <= read && read <= 0xBF)
break;// GBK

if (0xC0 <= read && read <= 0xDF) {
read = bis.read();
if (0x80 <= read && read <= 0xBF)
continue;
else
break;

} else if (0xE0 <= read && read <= 0xEF) {
read = bis.read();
if (0x80 <= read && read <= 0xBF) {
read = bis.read();
if (0x80 <= read && read <= 0xBF) {
charset = "UTF-8";
break;
} else
break;
} else
break;
}
}
}
bis.close();
} catch (Exception e) {
e.printStackTrace();
}
return charset;
}

/**
* 转换文件字符编码
* 步骤是先读取源文件的内容，存放到StringBuffer里面，
* 然后删除源文件，再重新new一个与源文件名一样的文件，再以另一种编码形式存放。
* @param path 文件绝对路径
* @param desCharset 想要转换的编码
* @throws Exception
*/
public static void convertEncoding (String path,String desCharset) throws Exception {
File srcFile = new File(path);
String srcCharset = getFileCharset(path); // 获取文件本来的字符编码
System.out.println(path + "的字符编码是" + srcCharset + "，要转成的字符编码是" + desCharset);
if(srcCharset.equalsIgnoreCase(desCharset)) {
System.out.println("编码相同，无需转换");
} else {
System.out.println("编码不同，需要转换");
InputStream in = new FileInputStream(path);
BufferedReader br = new BufferedReader(new InputStreamReader(in, srcCharset));
StringBuffer sb = new StringBuffer();
String s1;
while((s1 = br.readLine()) != null) {
String s = URLEncoder.encode(s1, desCharset);
sb.append(s + "\r\n"); // 一行+回车
}
br.close();
srcFile.delete(); // 删除原来的文件
// 重新以新编码写入文件并返回值
File desFile = new File(path); // 重新建原来的文件
desFile.createNewFile();
OutputStream out = new FileOutputStream(desFile);
OutputStreamWriter writer = new OutputStreamWriter(out, desCharset);
BufferedWriter bw = new BufferedWriter(writer);
bw.write(URLDecoder.decode(sb.toString(), desCharset));
bw.flush(); // 刷新到文件中
bw.close();
}
}

public static void main(String[] args) {
try {
String charset = getFileCharset("C:/Users/三浪/Desktop/99701200000_KFDB_DSMC_0402_20160304_I_4321_0001.XML");
System.out.println(charset);
convertEncoding("C:/Users/三浪/Desktop/1.txt", "utf-16");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}

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