示例#1
0
  public static void main(String args[]) throws IOException {
    if (args.length != 1) {
      System.err.println("Usage: java LockingExample <input file>");
      System.exit(0);
    }

    FileLock sharedLock = null;
    FileLock exclusiveLock = null;

    try {
      RandomAccessFile raf = new RandomAccessFile(args[0], "rw");

      // get the channel for the file
      FileChannel channel = raf.getChannel();

      System.out.println("trying to acquire lock ...");
      // this locks the first half of the file - exclusive
      exclusiveLock = channel.lock(0, raf.length() / 2, SHARED);
      System.out.println("lock acquired ...");

      /** Now modify the data . . . */
      try {
        // sleep for 10 seconds
        Thread.sleep(10000);
      } catch (InterruptedException ie) {
      }

      // release the lock
      exclusiveLock.release();
      System.out.println("lock released ...");

      // this locks the second half of the file - shared
      sharedLock = channel.lock(raf.length() / 2 + 1, raf.length(), SHARED);

      /** Now read the data . . . */

      // release the lock
      sharedLock.release();
    } catch (java.io.IOException ioe) {
      System.err.println(ioe);
    } finally {
      if (exclusiveLock != null) exclusiveLock.release();
      if (sharedLock != null) sharedLock.release();
    }
  }
示例#2
0
 public void run() {
   try {
     // Exclusive lock with no overlap:
     FileLock fl = fc.lock(start, end, false);
     System.out.println("Locked: " + start + " to " + end);
     // Perform modification:
     while (buff.position() < buff.limit() - 1) buff.put((byte) (buff.get() + 1));
     fl.release();
     System.out.println("Released: " + start + " to " + end);
   } catch (IOException e) {
     throw new RuntimeException(e);
   }
 }