Java example source code file (CountedTimerTaskUtils.java)

This example Java source code file (CountedTimerTaskUtils.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

countedtimertask, countedtimertaskutils, debug, util

The CountedTimerTaskUtils.java Java example source code

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

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);
    }
}