/*

 * Copyright (c) 2004, 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

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 */

package sun.jvmstat.perfdata.monitor;

import java.util.*;

/**

 * Utility methods for use with {@link CountedTimerTask} instances.

 *

 * @author Brian Doherty

 * @since 1.5

 */

public class CountedTimerTaskUtils {

    private static final boolean DEBUG = false;

    /**

     * Reschedule a CountedTimeTask at a different interval. Probably not

     * named correctly. This method cancels the old task and computes the

     * delay for starting the new task based on the new interval and the

     * time at which the old task was last executed.

     *

     * @param timer the Timer for the task

     * @param oldTask the old Task

     * @param newTask the new Task

     * @param oldInterval the old interval; use for debugging output

     *                    purposes only.

     * @param newInterval scheduling interval in milliseconds

     */

    public static void reschedule(Timer timer, CountedTimerTask oldTask,

                                  CountedTimerTask newTask, int oldInterval,

                                  int newInterval) {

        long now = System.currentTimeMillis();

        long lastRun = oldTask.scheduledExecutionTime();

        long expired = now - lastRun;

        if (DEBUG) {

            System.err.println("computing timer delay: "

                               + " oldInterval = " + oldInterval

                               + " newInterval = " + newInterval

                               + " samples = " + oldTask.executionCount()

                               + " expired = " + expired);

        }

        /*

         * check if original task ever ran - if not, then lastRun is

         * undefined and we simply set the delay to 0.

         */

        long delay = 0;

        if (oldTask.executionCount() > 0) {

            long remainder = newInterval - expired;

            delay = remainder >= 0 ? remainder : 0;

        }

        if (DEBUG) {

            System.err.println("rescheduling sampler task: interval = "

                               + newInterval

                               + " delay = " + delay);

        }

        timer.schedule(newTask, delay, newInterval);

    }

}