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LRUCache.javaAPI DocApache Tomcat 6.0.143703Fri Jul 20 04:20:32 BST 2007org.apache.tomcat.util.collections

LRUCache

public class LRUCache extends Object
This class implements a Generic LRU Cache
author
Ignacio J. Ortega

(Omit source code)

Fields Summary
private int
cacheSize
private Hashtable
nodes
private int
currentSize
private CacheNode
first
private CacheNode
last
Constructors Summary
public LRUCache(int i)

        currentSize = 0;
        cacheSize = i;
        nodes = new Hashtable(i);
Methods Summary
public voidclear()

        first = null;
        last = null;
public java.lang.Objectget(java.lang.Object key)

        CacheNode node = (CacheNode)nodes.get(key);
        if(node != null)
        {
            moveToHead(node);
            return node.value;
        }
        else
        {
            return null;
        }
private voidmoveToHead(org.apache.tomcat.util.collections.LRUCache$CacheNode node)

        if(node == first)
            return;
        if(node.prev != null)
            node.prev.next = node.next;
        if(node.next != null)
            node.next.prev = node.prev;
        if(last == node)
            last = node.prev;
        if(first != null)
        {
            node.next = first;
            first.prev = node;
        }
        first = node;
        node.prev = null;
        if(last == null)
            last = first;
public voidput(java.lang.Object key, java.lang.Object value)

        CacheNode node = (CacheNode)nodes.get(key);
        if(node == null)
        {
            if(currentSize >= cacheSize)
            {
                if(last != null)
                    nodes.remove(last.key);
                removeLast();
            }
            else
            {
                currentSize++;
            }
            node = new CacheNode();
        }
        node.value = value;
        node.key = key;
        moveToHead(node);
        nodes.put(key, node);
public java.lang.Objectremove(java.lang.Object key)

        CacheNode node = (CacheNode)nodes.get(key);
        if (node != null) {
            if (node.prev != null) {
                node.prev.next = node.next;
            }
            if (node.next != null) {
                node.next.prev = node.prev;
            }
            if (last == node)
                last = node.prev;
            if (first == node)
                first = node.next;
        }
        return node;
private voidremoveLast()

        if(last != null)
        {
            if(last.prev != null)
                last.prev.next = null;
            else
                first = null;
            last = last.prev;
        }