for (double x : VALUES) {
        assertBitEquals(prev, aa.get(i));
        assertFalse(aa.compareAndSet(i, unused, x));
        assertBitEquals(prev, aa.get(i));
        assertTrue(aa.compareAndSet(i, prev, x));
        assertBitEquals(x, aa.get(i));
        prev = x;
      }
    }
  }

  /** compareAndSet in one thread enables another waiting for value to succeed */

      assertBitEquals(x, at.doubleValue());
    }
  }

  /** compareAndSet treats +0.0 and -0.0 as distinct values */
  public void testDistinctZeros() {
    AtomicDouble at = new AtomicDouble(+0.0);
    assertFalse(at.compareAndSet(-0.0, 7.0));
    assertFalse(at.weakCompareAndSet(-0.0, 7.0));
    assertBitEquals(+0.0, at.get());
    assertTrue(at.compareAndSet(+0.0, -0.0));
    assertBitEquals(-0.0, at.get());

     * 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();
    T result = null;
    Throwable error = null;
    try {
      if (run) {

     * 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();
    T result = null;
    Throwable error = null;
    try {
      if (run) {

   * AtomicInteger's atomic operations, with some help from ConcurrentMap's atomic operations on
   * creation and removal (including automatic removal of zeroes). If the modification of an
   * AtomicInteger results in zero, we compareAndSet the value to zero; if that succeeds, we remove
   * the entry from the Map. If another operation sees a zero in the map, it knows that the entry is

    for (int i = 0; i < 10; i++) {
      final int expectedCount = i;
      list.add(
          new Runnable() {
            @Override
            public void run() {
              integer.compareAndSet(expectedCount, expectedCount + 1);
            }
          },
          directExecutor());
    }
    list.execute();
    assertEquals(10, integer.get());
  }

    for (int i = 0; i < 10; i++) {
      final int expectedCount = i;
      list.add(
          new Runnable() {
            @Override
            public void run() {
              integer.compareAndSet(expectedCount, expectedCount + 1);
            }
          },
          directExecutor());
    }
    list.execute();
    assertEquals(10, integer.get());
  }

   * test case failure. Only the first failure is recorded; subsequent calls to this method from
   * within the same test have no effect.
   */
  public void threadRecordFailure(Throwable t) {
    threadFailure.compareAndSet(null, t);
  }

  @Override
  public void setUp() {
    setDelays();
  }

  /**
   * Extra checks that get done for all test cases.
   *

   * test case failure. Only the first failure is recorded; subsequent calls to this method from
   * within the same test have no effect.
   */
  public void threadRecordFailure(Throwable t) {
    threadFailure.compareAndSet(null, t);
  }

  @Override
  public void setUp() {
    setDelays();
  }

  /**
   * Extra checks that get done for all test cases.
   *

        "Expected state to be %s, but it was %s",
        oldState,
        newState);
  }

  private boolean compareAndUpdateState(State oldState, State newState) {
    return state.compareAndSet(oldState, newState);
  }

  // TODO(dpb): Should we use a pair of ArrayLists instead of an IdentityHashMap?
  private static final class CloseableList extends IdentityHashMap<AutoCloseable, Executor>