JAVA: HOW TO AUTO-DETECT A FILE'S ENCODING
April 8, 2010 · by
George
· in
java
,
programming
·
3 Comments
Well, I don’t know if this is the best solution, but we can test the file against various CharsetDecodersand see if any of them reports no errors. Here is a class implementing this behaviour (note: the code below will open and read the file and test it against the decoder until EOF is reached – if an error occurs it proceeds to the next decoder etc. – so if you specify a great number of charsets to be tested, or test large files, it will be slow ) :
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/*
* 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.
*/
importjava.io.BufferedInputStream;
importjava.io.File;
importjava.io.FileInputStream;
importjava.io.FileNotFoundException;
importjava.io.IOException;
importjava.io.InputStreamReader;
importjava.nio.ByteBuffer;
importjava.nio.charset.CharacterCodingException;
importjava.nio.charset.Charset;
importjava.nio.charset.CharsetDecoder;
/**
*
*
@author
Georgios Migdos
*/
publicclassCharsetDetector {
publicCharset detectCharset(File f, String[] charsets) {
Charset charset =null;
for(String charsetName : charsets) {
charset = detectCharset(f, Charset.forName(charsetName));
if(charset !=null) {
break;
}
}
returncharset;
}
privateCharset detectCharset(File f, Charset charset) {
try{
BufferedInputStream input =newBufferedInputStream(newFileInputStream(f));
CharsetDecoder decoder = charset.newDecoder();
decoder.reset();
byte[] buffer =newbyte[512];
booleanidentified =false;
while((input.read(buffer) != -1) && (!identified)) {
identified = identify(buffer, decoder);
}
input.close();
if(identified) {
returncharset;
}else{
returnnull;
}
}catch(Exception e) {
returnnull;
}
}
privatebooleanidentify(byte[] bytes, CharsetDecoder decoder) {
try{
decoder.decode(ByteBuffer.wrap(bytes));
}catch(CharacterCodingException e) {
returnfalse;
}
returntrue;
}
publicstaticvoidmain(String[] args) {
File f =newFile("example.txt");
String[] charsetsToBeTested = {"UTF-8","windows-1253","ISO-8859-7"};
CharsetDetector cd =newCharsetDetector();
Charset charset = cd.detectCharset(f, charsetsToBeTested);
if(charset !=null) {
try{
InputStreamReader reader =newInputStreamReader(newFileInputStream(f), charset);
intc =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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