實現固定大小的hashMap（JAVA）

 

1、創建一個固定大小的hashMap

 

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

public class MaxSizeHashMap<K, V> extends LinkedHashMap<K, V> {
    private final int maxSize;

    public MaxSizeHashMap(int maxSize) {
        this.maxSize = maxSize;
    }


    //
    //Returns true if this map should remove its eldest entry. 
    //This method is invoked by put and putAll after inserting a new entry into the map. 
    //It provides the implementor with the opportunity to remove the eldest entry each time a new 
    //one is added. This is useful if the map represents a cache: 
    //    it allows the map to reduce memory consumption by deleting stale entries. 
    //
    @Override
    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
        return size() > maxSize;
    }
}

 

 

2、使用固定大小的hashMap

 

     @Test
    public void testMaxSizeMap(){
        MaxSizeHashMap<String,String> map = new MaxSizeHashMap<>(10);
        for(int i=0;i<100;i++){
            map.put(""+i,""+i);
        }
        System.out.println(map.size());  //10  保留最后存入map的10個數據
    }

 

 

參考地址

https://www.cnblogs.com/scottgu/p/4118428.html
https://blog.csdn.net/ClementAD/article/details/50596178