1 /*

     2  * Copyright (c) 2004, 2014, Oracle and/or its affiliates. All rights reserved.

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

     4  *

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

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

     7  * published by the Free Software Foundation.  Oracle designates this

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

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

    10  *

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

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

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

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

    15  * accompanied this code).

    16  *

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

    18  * 2 along with this work; if not, write to the Free Software Foundation,

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

    20  *

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

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

    23  * questions.

    24  */

    25 

    26 package sun.jvmstat.perfdata.monitor;

    27 

    28 import java.util.*;

    29 

    30 /**

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

    32  *

    33  * @author Brian Doherty

    34  * @since 1.5

    35  */

    36 public class CountedTimerTaskUtils {

    37 

    38     // 8028357 removed old, inefficient debug logging

    39 

    40     /**

    41      * Reschedule a CountedTimeTask at a different interval. Probably not

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

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

    44      * time at which the old task was last executed.

    45      *

    46      * @param timer the Timer for the task

    47      * @param oldTask the old Task

    48      * @param newTask the new Task

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

    50      *                    purposes only.

    51      * @param newInterval scheduling interval in milliseconds

    52      */

    53     public static void reschedule(Timer timer, CountedTimerTask oldTask,

    54                                   CountedTimerTask newTask, int oldInterval,

    55                                   int newInterval) {

    56 

    57         long now = System.currentTimeMillis();

    58         long lastRun = oldTask.scheduledExecutionTime();

    59         long expired = now - lastRun;

    60 

    61         /*

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

    63          * undefined and we simply set the delay to 0.

    64          */

    65         long delay = 0;

    66         if (oldTask.executionCount() > 0) {

    67             long remainder = newInterval - expired;

    68             delay = remainder >= 0 ? remainder : 0;

    69         }

    70 

    71         timer.schedule(newTask, delay, newInterval);

    72     }

    73 }