| J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2003 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package sun.misc; |
| 27 | |
| 28 | /** |
| 29 | * Utility class for small LRU caches. |
| 30 | * |
| 31 | * @author Mark Reinhold |
| 32 | */ |
| 33 | public abstract class LRUCache<N,V> { |
| 34 | |
| 35 | private V[] oa = null; |
| 36 | private final int size; |
| 37 | |
| 38 | public LRUCache(int size) { |
| 39 | this.size = size; |
| 40 | } |
| 41 | |
| 42 | abstract protected V create(N name); |
| 43 | |
| 44 | abstract protected boolean hasName(V ob, N name); |
| 45 | |
| 46 | public static void moveToFront(Object[] oa, int i) { |
| 47 | Object ob = oa[i]; |
| 48 | for (int j = i; j > 0; j--) |
| 49 | oa[j] = oa[j - 1]; |
| 50 | oa[0] = ob; |
| 51 | } |
| 52 | |
| 53 | public V forName(N name) { |
| 54 | if (oa == null) { |
| 55 | oa = (V[])new Object[size]; |
| 56 | } else { |
| 57 | for (int i = 0; i < oa.length; i++) { |
| 58 | V ob = oa[i]; |
| 59 | if (ob == null) |
| 60 | continue; |
| 61 | if (hasName(ob, name)) { |
| 62 | if (i > 0) |
| 63 | moveToFront(oa, i); |
| 64 | return ob; |
| 65 | } |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | // Create a new object |
| 70 | V ob = create(name); |
| 71 | oa[oa.length - 1] = ob; |
| 72 | moveToFront(oa, oa.length - 1); |
| 73 | return ob; |
| 74 | } |
| 75 | |
| 76 | } |