LRU:最近最久未使用

LRU:最近最久未使用
LinkedHashMap默认是不删除元素的,通过重写removeEldestEnrtry来实现最大容量

public class LRUMap<K,V> extends LinkedHashMap {

    private static final long serialVersionUID = 7712857012453857193L;

    //最大容量
    public static int MAX_SIZE=20;

    public LRUMap(int initialCapacity, float loadFactor,boolean accessOrder){
        super(initialCapacity, loadFactor, accessOrder);
    }

    /**
     * 如果Map的尺寸大于设定的最大容量,返回true
     * 再新加入对象时删除最老的对象
     */
    @Override
    protected boolean removeEldestEntry(Map.Entry eldest) {
        return size()>MAX_SIZE;
    }

    public static void main(String[] args) {
        Map<Integer,Integer> map = new LRUMap<>(10,0.75f,true);
        LRUMap.MAX_SIZE=3;
        map.put(1,1);
        map.put(2,2);
        map.put(3,3);
        map.put(4,4);
        map.put(5,5);
        System.out.println(map.size());
        for (Map.Entry<Integer,Integer> entry:map.entrySet()){
            System.out.println(entry.getKey()+":"+entry.getValue());
        }
    }
}

运行结果:

3
3:3
4:4
5:5