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| 1 | /* | ||
| 2 | * Copyright (c) 2004, 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 | private static final boolean DEBUG = false; | ||
| 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 | if (DEBUG) { | ||
| 62 | System.err.println("computing timer delay: " | ||
| 63 | + " oldInterval = " + oldInterval | ||
| 64 | + " newInterval = " + newInterval | ||
| 65 | + " samples = " + oldTask.executionCount() | ||
| 66 | + " expired = " + expired); | ||
| 67 | } | ||
| 68 | |||
| 69 | /* | ||
| 70 | * check if original task ever ran - if not, then lastRun is | ||
| 71 | * undefined and we simply set the delay to 0. | ||
| 72 | */ | ||
| 73 | long delay = 0; | ||
| 74 | if (oldTask.executionCount() > 0) { | ||
| 75 | long remainder = newInterval - expired; | ||
| 76 | delay = remainder >= 0 ? remainder : 0; | ||
| 77 | } | ||
| 78 | |||
| 79 | if (DEBUG) { | ||
| 80 | System.err.println("rescheduling sampler task: interval = " | ||
| 81 | + newInterval | ||
| 82 | + " delay = " + delay); | ||
| 83 | } | ||
| 84 | |||
| 85 | timer.schedule(newTask, delay, newInterval); | ||
| 86 | } | ||
| 87 | } | ||