public class ReentrantReadWriteLock implements ReadWriteLock, java.io.Serializable {
    private final ReentrantReadWriteLock.ReadLock readerLock;
    private final ReentrantReadWriteLock.WriteLock writerLock;
    final Sync sync; // sync = fair ? new FairSync() : new NonfairSync();

    abstract static class Sync extends AbstractQueuedSynchronizer {
        protected final boolean tryAcquire(int acquires);
        protected final boolean tryRelease(int releases);
        protected final int tryAcquireShared(int unused);
        protected final boolean tryReleaseShared(int unused);

        final boolean tryWriteLock();
        final boolean tryReadLock();
    }

    static final class NonfairSync extends Sync {
        final boolean writerShouldBlock();
        final boolean readerShouldBlock();
    }

    static final class FairSync extends Sync {
        final boolean writerShouldBlock();
        final boolean readerShouldBlock();
    }

    public static class ReadLock implements Lock, java.io.Serializable {
        protected ReadLock(ReentrantReadWriteLock lock);
        public void lock();
        public void unlock();
    }

    public static class WriteLock implements Lock, java.io.Serializable {
        protected WriteLock(ReentrantReadWriteLock lock);
        public void lock();
        public void unlock();
    }
}