001/*
002 * Copyright (C) 2010 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.util.concurrent;
016
017import com.google.common.annotations.GwtIncompatible;
018import com.google.common.collect.ForwardingQueue;
019import com.google.errorprone.annotations.CanIgnoreReturnValue;
020import java.util.Collection;
021import java.util.concurrent.BlockingQueue;
022import java.util.concurrent.TimeUnit;
023
024/**
025 * A {@link BlockingQueue} which forwards all its method calls to another {@link BlockingQueue}.
026 * Subclasses should override one or more methods to modify the behavior of the backing collection
027 * as desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator
028 * pattern</a>.
029 *
030 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
031 * default} methods. Instead, it inherits their default implementations. When those implementations
032 * invoke methods, they invoke methods on the {@code ForwardingBlockingQueue}.
033 *
034 * @author Raimundo Mirisola
035 * @param <E> the type of elements held in this collection
036 * @since 4.0
037 */
038@CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
039@GwtIncompatible
040public abstract class ForwardingBlockingQueue<E> extends ForwardingQueue<E>
041    implements BlockingQueue<E> {
042
043  /** Constructor for use by subclasses. */
044  protected ForwardingBlockingQueue() {}
045
046  @Override
047  protected abstract BlockingQueue<E> delegate();
048
049  @Override
050  public int drainTo(Collection<? super E> c, int maxElements) {
051    return delegate().drainTo(c, maxElements);
052  }
053
054  @Override
055  public int drainTo(Collection<? super E> c) {
056    return delegate().drainTo(c);
057  }
058
059  @Override
060  public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException {
061    return delegate().offer(e, timeout, unit);
062  }
063
064  @Override
065  public E poll(long timeout, TimeUnit unit) throws InterruptedException {
066    return delegate().poll(timeout, unit);
067  }
068
069  @Override
070  public void put(E e) throws InterruptedException {
071    delegate().put(e);
072  }
073
074  @Override
075  public int remainingCapacity() {
076    return delegate().remainingCapacity();
077  }
078
079  @Override
080  public E take() throws InterruptedException {
081    return delegate().take();
082  }
083}