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/*
 * Copyright 2009 Google Inc.
 *
 * 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.test.metric.collection;

import java.util.HashMap;
import java.util.Map;

import com.google.common.base.Supplier;
import com.google.common.collect.ForwardingMap;

/**
 * Wrap a Map to provide lazy creation of its values.
 * @author [email protected] (Alex Eagle)
 */
public class LazyHashMap extends ForwardingMap {
  private final Map delegate;
  private final Supplier supplier;

  public LazyHashMap(Supplier supplier) {
    this.delegate = new HashMap();
    this.supplier = supplier;
  }

  protected Map delegate() {
    return delegate;
  }

  @Override
  public V get(Object o) {
    V value = delegate.get(o);
    if (value == null) {
      value = supplier.get();
      delegate.put((K)o, value);
    }
    return value;
  }

  public static  Map newLazyHashMap(Supplier supplier) {
    return new LazyHashMap(supplier);
  }

}