/*
* Copyright 2000-2009 JetBrains s.r.o.
*
* 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.intellij.util.containers;
import java.lang.ref.WeakReference;
import java.util.concurrent.ConcurrentMap;
import static com.intellij.util.ObjectUtils.NULL;
/**
* @author peter
*/
public abstract class WeakFactoryMap<T,V> {
private final ConcurrentMap<T, WeakReference<V>> myMap = new ConcurrentWeakHashMap<T, WeakReference<V>>();
protected abstract V create(T key);
public final V get(T key) {
final WeakReference<V> reference = myMap.get(key);
if (reference != null) {
final V v = reference.get();
if (v != null) {
return v == NULL ? null : v;
}
}
final V value = create(key);
WeakReference<V> valueRef = new WeakReference<V>(value == null ? (V)NULL : value);
WeakReference<V> prevRef = myMap.putIfAbsent(key, valueRef);
V prev = prevRef == null ? null : prevRef.get();
return prev == null || prev == NULL ? value : prev;
}
public final boolean containsKey(T key) {
return myMap.containsKey(key);
}
public void clear() {
myMap.clear();
}
}