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| 1 | /* | ||
| 2 | * Copyright (c) 2003, Oracle and/or its affiliates. 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. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * 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 | } | ||