import java.util.LinkedHashMap;

import java.util.Map;

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

    private static final int MAX_CACHE_SIZE = 100;

    private int limit;

    public LRUCache() {

        this(MAX_CACHE_SIZE);

    }

    public LRUCache(int cacheSize) {

        super(cacheSize, 0.75f, true);

        this.limit = cacheSize;

    }

    public V save(K key, V val) {

        return put(key, val);

    }

    public V getOne(K key) {

        return get(key);

    }

    public boolean exists(K key) {

        return containsKey(key);

    }

    /**

     * 判断节点数是否超限

     * @param eldest

     * @return 超限返回 true，否则返回 false

     */

    @Override

    protected boolean removeEldestEntry(Map.Entry eldest) {

        return size() > limit;

    }

    @Override

    public String toString() {

        StringBuilder sb = new StringBuilder();

        for (Map.Entry<K, V> entry : entrySet()) {

            sb.append(String.format("%s:%s ", entry.getKey(), entry.getValue()));

        }

        return sb.toString();

    }

    public static void main(String[] args){

        LRUCache<String, Integer> cache = new LRUCache<>(3);

        for (int i = 0; i < 10; i++) {

            cache.save("I" + i, i * i);

        }

System.out.println(cache);

        System.out.println("插入10个键值对后，缓存内容为：");

        System.out.println(cache + "\n");

        System.out.println("访问键值为I8的节点后，缓存内容为：");

        cache.getOne("I8");

        System.out.println(cache + "\n");

        System.out.println("插入键值为I1的键值对后，缓存内容：");

        cache.save("I1", 1);

        System.out.println(cache);

        System.out.println("size:"+cache.size());

    }

}