Java Language Locking


A file can be locked using the FileChannel API that can be acquired from Input Output streams and readers

Example with streams

// Open a file stream FileInputStream ios = new FileInputStream(filename);

    // get underlying channel
    FileChannel channel = ios.getChannel();

     * try to lock the file. true means whether the lock is shared or not i.e. multiple processes can acquire a
     * shared lock (for reading only) Using false with readable channel only will generate an exception. You should
     * use a writable channel (taken from FileOutputStream) when using false. tryLock will always return immediately
    FileLock lock = channel.tryLock(0, Long.MAX_VALUE, true);

    if (lock == null) {
        System.out.println("Unable to acquire lock");
    } else {
        System.out.println("Lock acquired successfully");

    // you can also use blocking call which will block until a lock is acquired.

    // Once you have completed desired operations of file. release the lock
    if (lock != null) {

    // close the file stream afterwards
    // Example with reader
    RandomAccessFile randomAccessFile = new RandomAccessFile(filename,  "rw");
    FileChannel channel = randomAccessFile.getChannel();
    //repeat the same steps as above but now you can use shared as true or false as the channel is in read write mode