Binary file reader byte[] to string conversion gone wrong?

Question

I'm trying to display whats in the file header which should be text (the rest of the file is binary) but when I print strtemp I get this:

strTemp: ??????

Here is the code.

String fileName = "test.file";

URI logUri = new File(fileName).getAbsoluteFile().toURI();  

BufferedInputStream in = new BufferedInputStream(new FileInputStream(new File(logUri))); 

byte[] btemp = new byte[14];
in.read(btemp);

String strtemp = "";

for(int i = 0; i < btemp.length; i+= 2) {
    strtemp += String.valueOf((char)(((btemp[i]&0x00FF)<<8) + (btemp[i+1]&0x00FF)));
}

System.out.println("strTemp: " + strtemp);

How do I get strtemp to be whats in the file? and to display it properly?

What's in the file? characters? In which character encoding? How were they written? — JB Nizet
– JB Nizet, Commented Jun 12, 2012 at 8:48
why switch HIGH byte and LOW byte, is it multibyte character? is it little-endian? what's the charset encoding? — LiuYan 刘研
– LiuYan 刘研, Commented Jun 12, 2012 at 8:52

jontro · Accepted Answer · 2012-06-12 08:49:39Z

3

As you can see from the Constructor summary of http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/String.html you can initialize a String from bytes directly.

Also you should supply the charset you have in your source file.

answered Jun 12, 2012 at 8:49

jontro

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alain.janinm · Accepted Answer · 2012-06-12 09:01:23Z

0

For this kind of need you can use ByteBuffer and CharBuffer :

    FileChannel channel = new RandomAccessFile("/home/alain/toto.txt", "r").getChannel();
    //Map the 14 first bytes
    ByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, 14);
    //Set your charset here
    Charset chars = Charset.forName("ISO-8859-1");
    CharBuffer cbuf = chars.decode(buffer);
    System.out.println("str = " + cbuf.toString());

answered Jun 12, 2012 at 9:01

alain.janinm

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