# LRUCache.java

    /*
     *  Copyright (c) 2005-2011, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
     *
     *  WSO2 Inc. 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.wso2.carbon.governance.api.cache;

    import java.util.LinkedHashMap;
    import java.util.Map;
    import java.util.concurrent.locks.ReadWriteLock;
    import java.util.concurrent.locks.ReentrantReadWriteLock;

    public class LRUCache<K, V> extends LinkedHashMap<K, V> {

        int maxSize;

        private ReadWriteLock lock;

        public LRUCache(int maxSize) {
            super(maxSize + 1, 1, false);
            this.maxSize = maxSize;
            this.lock = new ReentrantReadWriteLock();
        }

        @Override
        public V get(Object key) {
            lock.readLock().lock();
            try {
                return super.get(key);
            } finally {
                lock.readLock().unlock();
            }
        }

        @Override
        public V put(K key, V value) {
            lock.writeLock().lock();
            try {
                return super.put(key, value);
            } finally {
                lock.writeLock().unlock();
            }
        }

        @Override
        public V remove(Object key) {
            lock.writeLock().lock();
            try {
                return super.remove(key);
            } finally {
                lock.writeLock().unlock();
            }
        }

        @Override
        public void clear() {
            lock.writeLock().lock();
            try {
                super.clear();
            } finally {
                lock.writeLock().unlock();
            }
        }

        @Override
        protected boolean removeEldestEntry(Map.Entry eldest) {
            boolean remove = size() > maxSize;
            if (remove) {
                handleRemovableEntry(eldest);
            }
            return remove;
        }

        protected void handleRemovableEntry(Map.Entry<K, V> entry) {

        }

        public void exclusiveLock() {
            lock.writeLock().lock();
        }

        public void release() {
            lock.writeLock().unlock();
        }

    }