| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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.apache.iotdb.tsfile.common.cache; |
| |
| import java.io.IOException; |
| import java.util.LinkedHashMap; |
| import java.util.Map; |
| |
| /** This class is not thread safe. */ |
| public abstract class LRUCache<K, T> implements Cache<K, T> { |
| |
| protected Map<K, T> cache; |
| |
| protected LRUCache(int cacheSize) { |
| this.cache = |
| new LinkedHashMap<K, T>(cacheSize, 0.75f, true) { |
| @Override |
| protected boolean removeEldestEntry(Map.Entry eldest) { |
| return size() > cacheSize; |
| } |
| }; |
| } |
| |
| @Override |
| public synchronized T get(K key) throws IOException { |
| if (cache.containsKey(key)) { |
| return cache.get(key); |
| } else { |
| T value = loadObjectByKey(key); |
| if (value != null) { |
| cache.put(key, value); |
| } |
| return value; |
| } |
| } |
| |
| @Override |
| public synchronized void clear() { |
| cache.clear(); |
| } |
| |
| public synchronized void put(K key, T value) { |
| cache.put(key, value); |
| } |
| |
| protected abstract T loadObjectByKey(K key) throws IOException; |
| |
| public synchronized void removeItem(K key) { |
| cache.remove(key); |
| } |
| } |