assertTrue(aa.compareAndSet(i, prev, x));
        assertBitEquals(x, aa.get(i));
        prev = x;
      }
    }
  }

  /** compareAndSet in one thread enables another waiting for value to succeed */
  public void testCompareAndSetInMultipleThreads() throws InterruptedException {
    final AtomicDoubleArray a = new AtomicDoubleArray(1);
    a.set(0, 1.0);
    Thread t =
        newStartedThread(

     * might be cancelled before we set the runner thread. That would make it impossible to
     * interrupt, yet it will still run, since interruptTask will leave the runner value null,
     * allowing the CAS below to succeed.
     */
    Thread currentThread = Thread.currentThread();
    if (!compareAndSet(null, currentThread)) {
      return; // someone else has run or is running.
    }

    boolean run = !isDone();

        assertTrue(aa.compareAndSet(i, prev, x));
        assertBitEquals(x, aa.get(i));
        prev = x;
      }
    }
  }

  /** compareAndSet in one thread enables another waiting for value to succeed */
  public void testCompareAndSetInMultipleThreads() throws InterruptedException {
    final AtomicDoubleArray a = new AtomicDoubleArray(1);
    a.set(0, 1.0);
    Thread t =
        newStartedThread(

      assertTrue(at.compareAndSet(prev, x));
      assertBitEquals(x, at.get());
      prev = x;
    }
  }

  /** compareAndSet in one thread enables another waiting for value to succeed */
  public void testCompareAndSetInMultipleThreads() throws Exception {
    final AtomicDouble at = new AtomicDouble(1.0);
    Thread t =
        newStartedThread(
            new CheckedRunnable() {

    // lockD -> lockA
    lockD.lock();
    lockA.lock();
    lockA.unlock();
    lockD.unlock();

    // lockA -> lockD should warn but otherwise succeed because lockD was
    // created by a factory with the WARN policy.
    lockA.lock();
    lockD.lock();
  }

  public void testReentrantLock_tryLock() throws Exception {

   * is permitted and similarly for decrease/remove(). We assume that a
   * setCount() no-op is permitted if either add() or remove() is permitted,
   * though we also allow it to "succeed" if neither is permitted.
   */

  private void assertSetCount(E element, int count) {
    setCountCheckReturnValue(element, count);

    assertEquals(

   * is permitted and similarly for decrease/remove(). We assume that a
   * setCount() no-op is permitted if either add() or remove() is permitted,
   * though we also allow it to "succeed" if neither is permitted.
   */

  private void assertSetCount(E element, int count) {
    setCountCheckReturnValue(element, count);

    assertEquals(

      long oldValue = atomic.get();
      if (oldValue == 0L || atomic.compareAndSet(oldValue, 0L)) {
        // only remove after setting to zero, to avoid concurrent updates
        map.remove(key, atomic);
        // succeed even if the remove fails, since the value was already adjusted
        return oldValue;
      }
    }
  }

  /**
   * If {@code (key, value)} is currently in the map, this method removes it and returns true;

      }
    }
  }

  /*
   * This next part consists of several sample classes that provide
   * demonstrations of conditions that cause NullPointerTester
   * to succeed/fail.
   */

  /** Lots of well-behaved methods. */
  @SuppressWarnings("unused") // used by reflection
  private static class PassObject extends SomeClassThatDoesNotUseNullable {

  private static final class TimedPutQueue {
    final BlockingQueue<String> queue;
    final Completion completed;

    /**
     * Creates a {@link EnableWrites} which open up a spot for a {@code put} to succeed in {@code
     * countdownInMillis}.
     */
    static TimedPutQueue createWithDelay(long countdownInMillis) {
      return new TimedPutQueue(countdownInMillis);
    }