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ComputingMap.java
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125 lines (99 loc) · 3.01 KB
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/*
* Copyright (c) 2008-2014 MongoDB, 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 org.bson.util;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
import static org.bson.util.Assertions.notNull;
final class ComputingMap<K, V> implements Map<K, V>, Function<K, V> {
public static <K, V> Map<K, V> create(Function<K, V> function) {
return new ComputingMap<K, V>(CopyOnWriteMap.<K, V> newHashMap(), function);
}
private final ConcurrentMap<K, V> map;
private final Function<K, V> function;
ComputingMap(ConcurrentMap<K, V> map, Function<K, V> function) {
this.map = notNull("map", map);
this.function = notNull("function", function);
}
public V get(Object key) {
while (true) {
V v = map.get(key);
if (v != null)
return v;
@SuppressWarnings("unchecked")
K k = (K) key;
V value = function.apply(k);
if (value == null)
return null;
map.putIfAbsent(k, value);
}
}
public V apply(K k) {
return get(k);
}
public V putIfAbsent(K key, V value) {
return map.putIfAbsent(key, value);
}
public boolean remove(Object key, Object value) {
return map.remove(key, value);
}
public boolean replace(K key, V oldValue, V newValue) {
return map.replace(key, oldValue, newValue);
}
public V replace(K key, V value) {
return map.replace(key, value);
}
public int size() {
return map.size();
}
public boolean isEmpty() {
return map.isEmpty();
}
public boolean containsKey(Object key) {
return map.containsKey(key);
}
public boolean containsValue(Object value) {
return map.containsValue(value);
}
public V put(K key, V value) {
return map.put(key, value);
}
public V remove(Object key) {
return map.remove(key);
}
public void putAll(Map<? extends K, ? extends V> m) {
map.putAll(m);
}
public void clear() {
map.clear();
}
public Set<K> keySet() {
return map.keySet();
}
public Collection<V> values() {
return map.values();
}
public Set<java.util.Map.Entry<K, V>> entrySet() {
return map.entrySet();
}
public boolean equals(Object o) {
return map.equals(o);
}
public int hashCode() {
return map.hashCode();
}
}