org.teamapps.dto.CopyOnWriteLeakyCache Maven / Gradle / Ivy
/*-
* ========================LICENSE_START=================================
* TeamApps
* ---
* Copyright (C) 2014 - 2023 TeamApps.org
* ---
* 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.
* =========================LICENSE_END==================================
*/
package org.teamapps.dto;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;
public class CopyOnWriteLeakyCache {
private Map map = Collections.emptyMap(); // invariant: this map is never directly modified, only copied!
public V computeIfAbsent(K key, Function computeFunction) {
V value = map.get(key);
if (value != null) {
return value;
} else {
HashMap mapCopy = new HashMap<>(map);
value = computeFunction.apply(key);
mapCopy.put(key, value);
map = mapCopy;
return value;
}
}
}