1 /*
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3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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.
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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).
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19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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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 
LRUCache(int size)38     public LRUCache(int size) {
39         this.size = size;
40     }
41 
create(N name)42     abstract protected V create(N name);
43 
hasName(V ob, N name)44     abstract protected boolean hasName(V ob, N name);
45 
moveToFront(Object[] oa, int i)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 
forName(N name)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