Cache.java

/**
 * Copyright (C) 2013-2015 all@code-story.net
 *
 * 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 net.codestory.http.misc;

import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;

public class Cache<K, V> implements Function<K, V> {
  private final Function<K, V> delegate;
  private final Map<K, V> keyValues;

  public Cache(Function<K, V> delegate) {
    this.delegate = delegate;
    this.keyValues = new ConcurrentHashMap<>();
  }

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