1 package org.apache.commons.jcs3.engine.memory.lru;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import java.io.IOException;
23
24 import org.apache.commons.jcs3.engine.behavior.ICacheElement;
25 import org.apache.commons.jcs3.engine.memory.AbstractDoubleLinkedListMemoryCache;
26 import org.apache.commons.jcs3.engine.memory.util.MemoryElementDescriptor;
27
28 /**
29 * A fast reference management system. The least recently used items move to the end of the list and
30 * get spooled to disk if the cache hub is configured to use a disk cache. Most of the cache
31 * bottlenecks are in IO. There are no io bottlenecks here, it's all about processing power.
32 * <p>
33 * Even though there are only a few adjustments necessary to maintain the double linked list, we
34 * might want to find a more efficient memory manager for large cache regions.
35 * <p>
36 * The LRUMemoryCache is most efficient when the first element is selected. The smaller the region,
37 * the better the chance that this will be the case. < .04 ms per put, p3 866, 1/10 of that per get
38 */
39 public class LRUMemoryCache<K, V>
40 extends AbstractDoubleLinkedListMemoryCache<K, V>
41 {
42 /**
43 * Puts an item to the cache. Removes any pre-existing entries of the same key from the linked
44 * list and adds this one first.
45 * <p>
46 * @param ce The cache element, or entry wrapper
47 * @return MemoryElementDescriptor the new node
48 * @throws IOException
49 */
50 @Override
51 protected MemoryElementDescriptor<K, V> adjustListForUpdate( final ICacheElement<K, V> ce )
52 throws IOException
53 {
54 return addFirst( ce );
55 }
56
57 /**
58 * Makes the item the first in the list.
59 * <p>
60 * @param me
61 */
62 @Override
63 protected void adjustListForGet( final MemoryElementDescriptor<K, V> me )
64 {
65 list.makeFirst( me );
66 }
67 }