File Locking!!! Is this a BUG or there is something wrong in my code.

Question

In new JDK v 1.4. new means of file locking are introuced, and it seems it is a little bit buggy yet (or maybe this one isn't a one). though it's better than nothing :)
here is 2 classes. first locks a file, the second attemts to change it.
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
class FileLocker {
  static File targetFile = new File ("D:\\Java",
                                     "manual.chm");
  public static void main(String[] args)
      throws Exception
    RandomAccessFile fin = new RandomAccessFile (targetFile, "rw");
    FileChannel fChan = fin.getChannel();
    FileLock lock = fChan.lock();
    // to let other process to attempt to change the same file.
    Thread.currentThread().sleep(100000);
    lock.release();
    fChan.close();
    fin.close();
}and the other class
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
class FileWriter {
  static File targetFile = new File ("D:\\Java",
                                     "manual.chm");
  public static void main(String[] args)
      throws Exception
    // this is better/more secure way to access files.
    RandomAccessFile f = new RandomAccessFile (targetFile, "rw");
    // next line deletes the file content even if file locked.
//    FileOutputStream f = new FileOutputStream (targetFile);
//--this parts is not needed as the problem is in first 2 lines
    FileChannel fChan = f.getChannel();
    if (fChan.isOpen()) {
      System.out.println("File is Opened, can't write");
    } else
      f.write(-1);
}so when i use FileInputStream for open stream to write,
constructor deletes the targetFile (makes it size equal to 0)
at once i create new FileInputStream object. Since, when i
use RandomAccessFile to open stream for writting nothing happens.
after that, f.write (-1); throws exception regardless the way the
uoutput stream was created.
So i think there is some problem in FileInputStream class' constructor.

Answer 1

OK, I know you mean FileOutputStream instead of FileInputStream in the above message. Looks to me like you've discovered a bug in the way Java is locking the file - locking the whole contents of a file (using the no-args lock or tryLock methods) doesn't prevent other programs, including Java, from overwriting some, if not all, of the file. Note that this occurs even on Windows 2000, where exclusive locks appear to be well supported.
I've found a similar problem where saving from Outlook appears to zero the whole of the locked file. Saving from other programs that are a little more careful, such as XEmacs, appears to only (!) truncate the file to 0, as the FileOutputStream does.
From what I can tell, in JDK 1.4.2 RandomAccessFiles respect each others' locks, but nothing else does.