SmallLRUCache.java

/*
 * Copyright 2014-2015 the original author or authors
 *
 * 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.wplatform.ddal.util;

import java.util.LinkedHashMap;
import java.util.Map;

/**
 * This class implements a small LRU object cache.
 *
 * @param <K> the key
 * @param <V> the value
 */
public class SmallLRUCache<K, V> extends LinkedHashMap<K, V> {

    private static final long serialVersionUID = 1L;
    private int size;

    private SmallLRUCache(int size) {
        super(size, (float) 0.75, true);
        this.size = size;
    }

    /**
     * Create a new object with all elements of the given collection.
     *
     * @param <K>  the key type
     * @param <V>  the value type
     * @param size the number of elements
     * @return the object
     */
    public static <K, V> SmallLRUCache<K, V> newInstance(int size) {
        return new SmallLRUCache<K, V>(size);
    }

    public void setMaxSize(int size) {
        this.size = size;
    }

    @Override
    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
        return size() > size;
    }

}