CharsetDetector

/*
 *  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
 * @author Fuze Sun
 */
public class CharsetDetector {
 
    public static 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 static 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 static 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.");
        }
    }
}