/*
 * %W% %E%
 *
 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package sun.misc;

/**
 * Utility class for small LRU caches.
 *
 * @author Mark Reinhold
 */
public abstract class LRUCache<N,V> {

    private V[] oa = null;
    private final int size;

    public LRUCache(int size) {
        this.size = size;
    }

    abstract protected V create(N name);

    abstract protected boolean hasName(V ob, N name);

    public static void moveToFront(Object[] oa, int i) {
        Object ob = oa[i];
        for (int j = i; j > 0; j--)
            oa[j] = oa[j - 1];
        oa[0] = ob;
    }

    public V forName(N name) {
        if (oa == null) {
            oa = (V[])new Object[size];
        } else {
            for (int i = 0; i < oa.length; i++) {
                V ob = oa[i];
                if (ob == null)
                    continue;
                if (hasName(ob, name)) {
                    if (i > 0)
                        moveToFront(oa, i);
                    return ob;
                }
            }
        }

        // Create a new object
        V ob = create(name);
        oa[oa.length - 1] = ob;
        moveToFront(oa, oa.length - 1);
        return ob;
    }

}