* test with reference to the same "lock-like object", and then their interactions with that object
 * are choreographed via the various methods on this class.
 *
 * <p>A "lock-like object" is really any object that may be used for concurrency control. If the
 * {@link #callAndAssertBlocks} method is ever called in a test, the lock-like object must have a

    }

    /*
     * This is an unsynchronized read! After the read, the function returns immediately or acquires
     * the lock to check again. Since an IDLE state was observed inside the preceding synchronized
     * block, and reference field assignment is atomic, this may save reacquiring the lock when
     * another thread or the worker task has cleared the count and set the state.
     *

    }

    @Override
    public E element() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.element();
    }

    @Override
    public Iterator<E> iterator() {
      // We explicitly don't lock for iterator()
      assertFalse(Thread.holdsLock(mutex));
      return delegate.iterator();
    }

    @Override
    public int size() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.size();

   * value, you should always choose it explicitly.
   *
   * <p>The current implementation uses the concurrency level to create a fixed number of hashtable
   * segments, each governed by its own write lock. The segment lock is taken once for each explicit
   * write, and twice for each cache loading computation (once prior to loading the new value, and
   * once after loading completes). Much internal cache management is performed at the segment

    service.addListener(new RecordingListener(service), directExecutor());
    Thread thread =
        new Thread() {
          @Override
          public void run() {
            // Internally stopAsync() grabs a lock, this could be any such method on
            // AbstractService.
            service.stopAsync();
          }
        };
    thread.start();
    thread.join(LONG_TIMEOUT_MILLIS);

   * object to facilitate testing.
   */
  private final SleepingStopwatch stopwatch;

  // Can't be initialized in the constructor because mocks don't call the constructor.
  @CheckForNull private volatile Object mutexDoNotUseDirectly;

  private Object mutex() {
    Object mutex = mutexDoNotUseDirectly;
    if (mutex == null) {
      synchronized (this) {

import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit test for {@link NullPointerTester}.
 *
 * @author Kevin Bourrillion
 * @author Mick Killianey
 */
@SuppressWarnings("CheckReturnValue")
public class NullPointerTesterTest extends TestCase {

  /** Non-NPE RuntimeException. */
  public static class FooException extends RuntimeException {

   * value, you should always choose it explicitly.
   *
   * <p>The current implementation uses the concurrency level to create a fixed number of hashtable
   * segments, each governed by its own write lock. The segment lock is taken once for each explicit
   * write, and twice for each cache loading computation (once prior to loading the new value, and
   * once after loading completes). Much internal cache management is performed at the segment

        .add(new Striped.SmallLazyStriped<ReadWriteLock>(50, READ_WRITE_LOCK_SUPPLIER))
        .add(new Striped.SmallLazyStriped<ReadWriteLock>(64, READ_WRITE_LOCK_SUPPLIER))
        .add(new Striped.LargeLazyStriped<ReadWriteLock>(50, READ_WRITE_LOCK_SUPPLIER))
        .add(new Striped.LargeLazyStriped<ReadWriteLock>(64, READ_WRITE_LOCK_SUPPLIER))
        .add(new Striped.SmallLazyStriped<Lock>(50, LOCK_SUPPLER))

  }

  @Benchmark
  void unorderedCycleDetectingLocks(int reps) {
    lockAndUnlock(factory.newReentrantLock("foo"), reps);
  }

  private static void lockAndUnlock(Lock lock, int reps) {
    for (int i = 0; i < reps; i++) {
      lock.lock();
      lock.unlock();
    }
  }

  @Benchmark
  void orderedPlainLocks(int reps) {
    lockAndUnlockNested(plainLocks, reps);
  }

  @Benchmark