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 } 77
