LRU Map : Map « Collections Data Structure « Java


 * @(#)$Id: 3619 2008-03-26 07:23:03Z yui $
 * Copyright 2006-2008 Makoto YUI
 * 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * Contributors:
 *     Makoto YUI - initial implementation
//package xbird.util.collections;

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

 * <DIV lang="en"></DIV>
 * <DIV lang="ja"></DIV>
 * @author Makoto YUI (
public class LRUMap<K, V> extends LinkedHashMap<K, V> {
    private static final long serialVersionUID = 1L;

    protected final int maxCapacity;

    public LRUMap(int maxCapacity) {
        super(maxCapacity, 1.0f, true);
        this.maxCapacity = maxCapacity;

    protected boolean removeEldestEntry(Entry<K, V> eldest) {
        return size() > maxCapacity;

    public void writeTo(ObjectOutput out) throws IOException {
        int size = size();
        for(Entry<K, V> e : entrySet()) {

    public static <K, V> LRUMap<K, V> readFrom(ObjectInput in) throws IOException,
            ClassNotFoundException {
        int cap = in.readInt();
        final LRUMap<K, V> map = new LRUMap<K, V>(cap);
        final int size = in.readInt();
        for(int i = 0; i < size; i++) {
            K key = (K) in.readObject();
            V value = (V) in.readObject();
            map.put(key, value);
        return map;



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