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package sun.jvmstat.perfdata.monitor;

import java.util.*;

Utility methods for use with CountedTimerTask instances. 
Author:
Brian Doherty
Since:
1.5/**
 * 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.
Params:
timer – the Timer for the task
oldTask – the old Task
newTask – the new Task
oldInterval – the old interval; use for debugging output
                   purposes only.
newInterval – scheduling interval in milliseconds/**
     * 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);
    }
}