LRU 算法

来源：互联网发布：plc编码器编程编辑：程序博客网时间：2024/05/22 13:54

最近在工作中遇到LRU算法，本人写了个实现，供大家参考，吐槽。

public class CacheLRU<K,V>{

private int maxSize=10;
private HashMap<K,Entry> map=new HashMap<K,Entry>();

public CacheLRU(int size){
this.maxSize=size;
}

private Entry head=null;
private Entry tail=null;

public void put(K key,V value){
Entry entry=new Entry();
entry.key=key;
entry.value=value;
putEntryToHead(entry);
}

public V get(K key){
Entry<K,V> result=null;
result=map.get(key);
if(result==null){
return null;
}else{
if(head==result){
return result.value;
}else{
if(tail==result){
tail=tail.pre;
tail.next=null;
} else{
result.next.pre=result.pre;
result.pre.next=result.next;
}
}
map.remove(result.key);
putEntryToHead(result);
return result.value;
}
}

private void putEntryToHead(Entry<K,V> entry){
map.put(entry.key,entry);
if(head==null){
head=entry;
tail=entry;
}else{
entry.pre=null;
entry.next=head;
head.pre=entry;
head=entry;
}
if(map.size()>maxSize){
map.remove(tail.key);
tail=tail.pre;
tail.next.pre=null;
tail.next=null;

}
}

public void getAllElements(){

if(head==null){
System.out.print("null");
}else{
Entry curr=head;
StringBuffer sb=new StringBuffer();
while (curr!=null){
sb.append(curr.key);
curr=curr.next;
}
System.out.println(sb.toString());
}
}

class Entry<K,V>{

Entry next;
Entry pre;
V value;
K key;
}

public static void main(String ag[]){
CacheLRU<String,String> lru=new CacheLRU<String,String>(3);
//lru.getAllElements();
lru.put("3","33");
lru.put("4","44");
lru.put("5","55");
System.out.println(lru.get("3"));
lru.put("6","66");
System.out.println(lru.get("5"));
System.out.println(lru.map.size());
lru.put("7","777");
lru.getAllElements();
}
}

0 0