#vulnerable code 
                              @Test
  public void testAsynchronousClose() throws IOException, InterruptedException {
    RegularFile file = regularFile(10);
    final FileChannel channel = channel(file, READ, WRITE);

    file.writeLock().lock(); // ensure all operations on the channel will block

    ExecutorService executor = Executors.newCachedThreadPool();

    List<Future<?>> futures = queueAllBlockingOperations(channel, executor);

    // ensure time for operations to start blocking
    Uninterruptibles.sleepUninterruptibly(10, MILLISECONDS);

    channel.close();

    for (Future<?> future : futures) {
      try {
        future.get();
        fail();
      } catch (ExecutionException expected) {
        assertTrue(expected.getCause() instanceof AsynchronousCloseException);
      }
    }
  } 
                            #location 3 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                              @Test
  public void testAsynchronousClose() throws Exception {
    RegularFile file = regularFile(10);
    final FileChannel channel = channel(file, READ, WRITE);

    file.writeLock().lock(); // ensure all operations on the channel will block

    ExecutorService executor = Executors.newCachedThreadPool();

    CountDownLatch latch = new CountDownLatch(BLOCKING_OP_COUNT);
    List<Future<?>> futures = queueAllBlockingOperations(channel, executor, latch);

    // wait for all the threads to have started running
    latch.await();
    // then ensure time for operations to start blocking
    Uninterruptibles.sleepUninterruptibly(20, MILLISECONDS);

    // close channel on this thread
    channel.close();

    // the blocking operations are running on different threads, so they all get
    // AsynchronousCloseException
    for (Future<?> future : futures) {
      try {
        future.get();
        fail();
      } catch (ExecutionException expected) {
        assertThat(expected.getCause()).named("blocking thread exception")
            .isA(AsynchronousCloseException.class);
      }
    }
  }