/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.cache;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import java.util.concurrent.ExecutionException;

A cache which forwards all its method calls to another cache. Subclasses should override one or
more methods to modify the behavior of the backing cache as desired per the decorator pattern.
Note that get, getUnchecked, and apply all expose the same underlying functionality, so should probably be overridden as a group. 
Author:
Charles Fry
Since:
11.0/**
 * A cache which forwards all its method calls to another cache. Subclasses should override one or
 * more methods to modify the behavior of the backing cache as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p>Note that {@link #get}, {@link #getUnchecked}, and {@link #apply} all expose the same
 * underlying functionality, so should probably be overridden as a group.
 *
 * @author Charles Fry
 * @since 11.0
 */
@GwtIncompatible
public abstract class ForwardingLoadingCache<K, V> extends ForwardingCache<K, V>
    implements LoadingCache<K, V> {

  
Constructor for use by subclasses. /** Constructor for use by subclasses. */
  protected ForwardingLoadingCache() {}

  @Override
  protected abstract LoadingCache<K, V> delegate();

  @Override
  public V get(K key) throws ExecutionException {
    return delegate().get(key);
  }

  @Override
  public V getUnchecked(K key) {
    return delegate().getUnchecked(key);
  }

  @Override
  public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException {
    return delegate().getAll(keys);
  }

  @Override
  public V apply(K key) {
    return delegate().apply(key);
  }

  @Override
  public void refresh(K key) {
    delegate().refresh(key);
  }

  
A simplified version of ForwardingLoadingCache where subclasses can pass in an already constructed LoadingCache as the delegate. 
Since:
10.0/**
   * A simplified version of {@link ForwardingLoadingCache} where subclasses can pass in an already
   * constructed {@link LoadingCache} as the delegate.
   *
   * @since 10.0
   */
  public abstract static class SimpleForwardingLoadingCache<K, V>
      extends ForwardingLoadingCache<K, V> {
    private final LoadingCache<K, V> delegate;

    protected SimpleForwardingLoadingCache(LoadingCache<K, V> delegate) {
      this.delegate = Preconditions.checkNotNull(delegate);
    }

    @Override
    protected final LoadingCache<K, V> delegate() {
      return delegate;
    }
  }
}