/*

 * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

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) {

            @SuppressWarnings("unchecked")

            V[] temp = (V[])new Object[size];

            oa = temp;

        } 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;

    }

}