Java自动探测文件的字符编码

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

import org.mozilla.intl.chardet.nsDetector;
import org.mozilla.intl.chardet.nsICharsetDetectionObserver;

public class FileCharsetDetector {
private boolean found = false;
private String encoding = null;

public static void main(String[] argv) throws Exception {
File file1 = new File("C:\\test1.txt");

System.out.println("文件编码:" + new FileCharsetDetector().guessFileEncoding(file1));
}

/**
* 传入一个文件(File)对象，检查文件编码
*
* @param file
*            File对象实例
* @return 文件编码，若无，则返回null
* @throws FileNotFoundException
* @throws IOException
*/
public String guessFileEncoding(File file) throws FileNotFoundException, IOException {
return guessFileEncoding(file, new nsDetector());
}

/**
* <pre>
* 获取文件的编码
* @param file
*            File对象实例
* @param languageHint
*            语言提示区域代码 @see #nsPSMDetector ,取值如下：
*             1 : Japanese
*             2 : Chinese
*             3 : Simplified Chinese
*             4 : Traditional Chinese
*             5 : Korean
*             6 : Dont know(default)
* </pre>
*
* @return 文件编码，eg：UTF-8,GBK,GB2312形式(不确定的时候，返回可能的字符编码序列)；若无，则返回null
* @throws FileNotFoundException
* @throws IOException
*/
public String guessFileEncoding(File file, int languageHint) throws FileNotFoundException, IOException {
return guessFileEncoding(file, new nsDetector(languageHint));
}

/**
* 获取文件的编码
*
* @param file
* @param det
* @return
* @throws FileNotFoundException
* @throws IOException
*/
private String guessFileEncoding(File file, nsDetector det) throws FileNotFoundException, IOException {
// Set an observer...
// The Notify() will be called when a matching charset is found.
det.Init(new nsICharsetDetectionObserver() {
public void Notify(String charset) {
encoding = charset;
found = true;
}
});

BufferedInputStream imp = new BufferedInputStream(new FileInputStream(file));
byte[] buf = new byte[1024];
int len;
boolean done = false;
boolean isAscii = false;

while ((len = imp.read(buf, 0, buf.length)) != -1) {
// Check if the stream is only ascii.
isAscii = det.isAscii(buf, len);
if (isAscii) {
break;
}
// DoIt if non-ascii and not done yet.
done = det.DoIt(buf, len, false);
if (done) {
break;
}
}
imp.close();
det.DataEnd();

if (isAscii) {
encoding = "ASCII";
found = true;
}

if (!found) {
String[] prob = det.getProbableCharsets();
//这里将可能的字符集组合起来返回
for (int i = 0; i < prob.length; i++) {
if (i == 0) {
encoding = prob[i];
} else {
encoding += "," + prob[i];
}
}

if (prob.length > 0) {
// 在没有发现情况下,也可以只取第一个可能的编码,这里返回的是一个可能的序列
return encoding;
} else {
return null;
}
}
return encoding;
}
}