java基于Hash表和双向链表简单实现LRU Cache
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package lru; import java.util.HashMap; public class LRUCache2<K,V> { public final int capacity; class DNode{ K key; V value; DNode next; DNode pre; public DNode(K key, V value, LRUCache2<K, V>.DNode pre, LRUCache2<K, V>.DNode next) { super(); this.key = key; this.value = value; this.pre = pre; this.next = next; } }
//附加头结点 DNode head=new DNode(null,null,null,null); DNode last=head; HashMap<K,DNode> map=new HashMap<>(); public LRUCache2(int capacity) { this.capacity=capacity; } public V get(K key) { DNode node=map.get(key); if(node!=null) { moveToHead(node); } return node==null?null:node.value; } public void put(K key, V value) { DNode node=map.get(key); if(node==null) { if(map.size()>=capacity) { removeLast(); } node=new DNode(key, value,head,head.next); if(head.next!=null) head.next.pre=node; head.next=node; map.put(node.key, node); if(last==head) last=node; }else { node.value=value; moveToHead(node); } } private void removeLast() { // TODO Auto-generated method stub if(last==null) { throw new IllegalArgumentException("cant remove before put"); } map.remove(last.key); last.pre.next=null; last=last.pre; } private void moveToHead(LRUCache2<K, V>.DNode node) { // TODO Auto-generated method stub if(head.next==node) return; if(last==node) { last=node.pre; } node.pre.next=node.next; if(node.next!=null) node.next.pre=node.pre; node.next=head.next; node.pre=head; head.next.pre=node; head.next=node; } }
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