// Establish an ordering from writeLockA -> writeLockB.
    writeLockA.lock();
    writeLockB.lock();
    writeLockB.unlock();
    writeLockA.unlock();

    // Establish an ordering from writeLockB -> writeLockC.
    writeLockB.lock();
    writeLockC.lock();
    writeLockB.unlock();

    // writeLockC -> writeLockA should fail.
    PotentialDeadlockException expected =

    // Establish an ordering from writeLockA -> writeLockB.
    writeLockA.lock();
    writeLockB.lock();
    writeLockB.unlock();
    writeLockA.unlock();

    // Establish an ordering from writeLockB -> writeLockC.
    writeLockB.lock();
    writeLockC.lock();
    writeLockB.unlock();

    // writeLockC -> writeLockA should fail.
    PotentialDeadlockException expected =

      this.writeLock = new CycleDetectingReentrantWriteLock(this);
      this.lockGraphNode = Preconditions.checkNotNull(lockGraphNode);
    }

    ///// Overridden ReentrantReadWriteLock methods. /////

    @Override
    public ReadLock readLock() {
      return readLock;
    }

    @Override
    public WriteLock writeLock() {
      return writeLock;
    }

    }

    @Override
    public Lock readLock() {
      return new WeakSafeLock(delegate.readLock(), this);
    }

    @Override
    public Lock writeLock() {
      return new WeakSafeLock(delegate.writeLock(), this);
    }
  }

  /** Lock object that ensures a strong reference is retained to a specified object. */
  private static final class WeakSafeLock extends ForwardingLock {