How to auto-detect a file's encoding
/*
* Copyright 2010 Georgios Migdos <cyberpython@gmail.com>.
*
* 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 <cyberpython@gmail.com>
*/
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.");
}
}
}
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