LinkedHashMap 最远未被使用丢弃缓存算法Least Recently used

编程技术  /  houtizong 发布于 3年前   85

直接贴代码

类：Test
类： LeastRecentlyUsedLinkedHashMap<K,V>


import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
public class Test {
public static void main(String[] args) {
/**
* LinkedHashMap 实现了Least Recently used 最远未被使用丢弃缓存算法
* :在固定大小的LinkedHashMap中如果容量大于了 size() 将丢弃最远时间未被使用的key value 是一种缓存算法
*/

LeastRecentlyUsedLinkedHashMap<String, String> lruMap = new
LeastRecentlyUsedLinkedHashMap<String, String>(5);
lruMap.put("1", "a");
lruMap.put("2", "ab");
lruMap.put("3", "abc");
lruMap.put("4", "abcd");
lruMap.put("5", "abcde");
lruMap.put("6", "abcdef");
lruMap.put("7", "abcdefg");

printMapContent(lruMap);

System.out.println("\n");
lruMap.get("3");
printMapContent(lruMap);

System.out.println("\n");
lruMap.put("8", "xxxxxx");
printMapContent(lruMap);

}

/**
* map循环
* @param lruMap
*/
public static void printMapContent(LeastRecentlyUsedLinkedHashMap lruMap){

Set<Map.Entry<String,String>>  entrySet = lruMap.entrySet();

Iterator iter = entrySet.iterator();

Map.Entry<String,String> entry = null;

while(iter.hasNext()){
entry = (Entry<String, String>) iter.next();
System.out.println("key: " + entry.getKey()+"  value: " +entry.getValue());
}
}
}



LRU算法实现类：


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

/**
*
*/
private static final long serialVersionUID = 1L;

/*指定map规定缓存容器长度*/
private int capacity;

LeastRecentlyUsedLinkedHashMap(int capacity){
super(capacity,0.75f,true);
this.capacity = capacity;
}


protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
return size()> capacity;
}

}