LRU实现

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

/**
 * LRU (Least Recently Used)
 */
public class LRUCache<K, V> extends LinkedHashMap<K, V> {

    private static final long serialVersionUID = 1L;
    //缓存大小
    private int cacheSize;

    public LRUCache(int cacheSize) {
        //第三个参数true是关键
        super(10, 0.75f, true);
        this.cacheSize = cacheSize;
    }

    /**
     * 缓存是否已满
     */
    @Override
    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
        boolean r = size() > cacheSize;
        if(r){
            System.out.println("清除缓存key："+eldest.getKey());
        }
        return r;
    }

    //测试
    public static void main(String[] args) {
        LRUCache<String, String> cache = new LRUCache<String, String>(5);
        cache.put("1", "1");
        cache.put("2", "2");
        cache.put("3", "3");
        cache.put("4", "4");
        cache.put("5", "5");

        System.out.println("初始化：");
        System.out.println(cache.keySet());
        System.out.println("访问3：");
        cache.get("3");
        System.out.println(cache.keySet());
        System.out.println("访问2：");
        cache.get("2");
        System.out.println(cache.keySet());
        System.out.println("增加数据6,7：");
        cache.put("6", "6");
        cache.put("7", "7");
        System.out.println(cache.keySet());
    }
}