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| 1 | /* | ||
| 2 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 3 | * | ||
| 4 | * This code is free software; you can redistribute it and/or modify it | ||
| 5 | * under the terms of the GNU General Public License version 2 only, as | ||
| 6 | * published by the Free Software Foundation. Oracle designates this | ||
| 7 | * particular file as subject to the "Classpath" exception as provided | ||
| 8 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 9 | * | ||
| 10 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 11 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 12 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 13 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 14 | * accompanied this code). | ||
| 15 | * | ||
| 16 | * You should have received a copy of the GNU General Public License version | ||
| 17 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 18 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 19 | * | ||
| 20 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 21 | * or visit www.oracle.com if you need additional information or have any | ||
| 22 | * questions. | ||
| 23 | */ | ||
| 24 | |||
| 25 | /* | ||
| 26 | * This file is available under and governed by the GNU General Public | ||
| 27 | * License version 2 only, as published by the Free Software Foundation. | ||
| 28 | * However, the following notice accompanied the original version of this | ||
| 29 | * file: | ||
| 30 | * | ||
| 31 | * Written by Doug Lea with assistance from members of JCP JSR-166 | ||
| 32 | * Expert Group and released to the public domain, as explained at | ||
| 33 | * http://creativecommons.org/publicdomain/zero/1.0/ | ||
| 34 | */ | ||
| 35 | |||
| 36 | package java.util.concurrent; | ||
| 37 | import java.util.concurrent.atomic.*; | ||
| 38 | import java.util.*; | ||
| 39 | |||
| 40 | /** | ||
| 41 | * An {@link ExecutorService} that can schedule commands to run after a given | ||
| 42 | * delay, or to execute periodically. | ||
| 43 | * | ||
| 44 | * <p> The <tt>schedule</tt> methods create tasks with various delays | ||
| 45 | * and return a task object that can be used to cancel or check | ||
| 46 | * execution. The <tt>scheduleAtFixedRate</tt> and | ||
| 47 | * <tt>scheduleWithFixedDelay</tt> methods create and execute tasks | ||
| 48 | * that run periodically until cancelled. | ||
| 49 | * | ||
| 50 | * <p> Commands submitted using the {@link Executor#execute} and | ||
| 51 | * {@link ExecutorService} <tt>submit</tt> methods are scheduled with | ||
| 52 | * a requested delay of zero. Zero and negative delays (but not | ||
| 53 | * periods) are also allowed in <tt>schedule</tt> methods, and are | ||
| 54 | * treated as requests for immediate execution. | ||
| 55 | * | ||
| 56 | * <p>All <tt>schedule</tt> methods accept <em>relative</em> delays and | ||
| 57 | * periods as arguments, not absolute times or dates. It is a simple | ||
| 58 | * matter to transform an absolute time represented as a {@link | ||
| 59 | * java.util.Date} to the required form. For example, to schedule at | ||
| 60 | * a certain future <tt>date</tt>, you can use: <tt>schedule(task, | ||
| 61 | * date.getTime() - System.currentTimeMillis(), | ||
| 62 | * TimeUnit.MILLISECONDS)</tt>. Beware however that expiration of a | ||
| 63 | * relative delay need not coincide with the current <tt>Date</tt> at | ||
| 64 | * which the task is enabled due to network time synchronization | ||
| 65 | * protocols, clock drift, or other factors. | ||
| 66 | * | ||
| 67 | * The {@link Executors} class provides convenient factory methods for | ||
| 68 | * the ScheduledExecutorService implementations provided in this package. | ||
| 69 | * | ||
| 70 | * <h3>Usage Example</h3> | ||
| 71 | * | ||
| 72 | * Here is a class with a method that sets up a ScheduledExecutorService | ||
| 73 | * to beep every ten seconds for an hour: | ||
| 74 | * | ||
| 75 | * <pre> {@code | ||
| 76 | * import static java.util.concurrent.TimeUnit.*; | ||
| 77 | * class BeeperControl { | ||
| 78 | * private final ScheduledExecutorService scheduler = | ||
| 79 | * Executors.newScheduledThreadPool(1); | ||
| 80 | * | ||
| 81 | * public void beepForAnHour() { | ||
| 82 | * final Runnable beeper = new Runnable() { | ||
| 83 | * public void run() { System.out.println("beep"); } | ||
| 84 | * }; | ||
| 85 | * final ScheduledFuture<?> beeperHandle = | ||
| 86 | * scheduler.scheduleAtFixedRate(beeper, 10, 10, SECONDS); | ||
| 87 | * scheduler.schedule(new Runnable() { | ||
| 88 | * public void run() { beeperHandle.cancel(true); } | ||
| 89 | * }, 60 * 60, SECONDS); | ||
| 90 | * } | ||
| 91 | * }}</pre> | ||
| 92 | * | ||
| 93 | * @since 1.5 | ||
| 94 | * @author Doug Lea | ||
| 95 | */ | ||
| 96 | public interface ScheduledExecutorService extends ExecutorService { | ||
| 97 | |||
| 98 | /** | ||
| 99 | * Creates and executes a one-shot action that becomes enabled | ||
| 100 | * after the given delay. | ||
| 101 | * | ||
| 102 | * @param command the task to execute | ||
| 103 | * @param delay the time from now to delay execution | ||
| 104 | * @param unit the time unit of the delay parameter | ||
| 105 | * @return a ScheduledFuture representing pending completion of | ||
| 106 | * the task and whose <tt>get()</tt> method will return | ||
| 107 | * <tt>null</tt> upon completion | ||
| 108 | * @throws RejectedExecutionException if the task cannot be | ||
| 109 | * scheduled for execution | ||
| 110 | * @throws NullPointerException if command is null | ||
| 111 | */ | ||
| 112 | public ScheduledFuture<?> schedule(Runnable command, | ||
| 113 | long delay, TimeUnit unit); | ||
| 114 | |||
| 115 | /** | ||
| 116 | * Creates and executes a ScheduledFuture that becomes enabled after the | ||
| 117 | * given delay. | ||
| 118 | * | ||
| 119 | * @param callable the function to execute | ||
| 120 | * @param delay the time from now to delay execution | ||
| 121 | * @param unit the time unit of the delay parameter | ||
| 122 | * @return a ScheduledFuture that can be used to extract result or cancel | ||
| 123 | * @throws RejectedExecutionException if the task cannot be | ||
| 124 | * scheduled for execution | ||
| 125 | * @throws NullPointerException if callable is null | ||
| 126 | */ | ||
| 127 | public <V> ScheduledFuture<V> schedule(Callable<V> callable, | ||
| 128 | long delay, TimeUnit unit); | ||
| 129 | |||
| 130 | /** | ||
| 131 | * Creates and executes a periodic action that becomes enabled first | ||
| 132 | * after the given initial delay, and subsequently with the given | ||
| 133 | * period; that is executions will commence after | ||
| 134 | * <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then | ||
| 135 | * <tt>initialDelay + 2 * period</tt>, and so on. | ||
| 136 | * If any execution of the task | ||
| 137 | * encounters an exception, subsequent executions are suppressed. | ||
| 138 | * Otherwise, the task will only terminate via cancellation or | ||
| 139 | * termination of the executor. If any execution of this task | ||
| 140 | * takes longer than its period, then subsequent executions | ||
| 141 | * may start late, but will not concurrently execute. | ||
| 142 | * | ||
| 143 | * @param command the task to execute | ||
| 144 | * @param initialDelay the time to delay first execution | ||
| 145 | * @param period the period between successive executions | ||
| 146 | * @param unit the time unit of the initialDelay and period parameters | ||
| 147 | * @return a ScheduledFuture representing pending completion of | ||
| 148 | * the task, and whose <tt>get()</tt> method will throw an | ||
| 149 | * exception upon cancellation | ||
| 150 | * @throws RejectedExecutionException if the task cannot be | ||
| 151 | * scheduled for execution | ||
| 152 | * @throws NullPointerException if command is null | ||
| 153 | * @throws IllegalArgumentException if period less than or equal to zero | ||
| 154 | */ | ||
| 155 | public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, | ||
| 156 | long initialDelay, | ||
| 157 | long period, | ||
| 158 | TimeUnit unit); | ||
| 159 | |||
| 160 | /** | ||
| 161 | * Creates and executes a periodic action that becomes enabled first | ||
| 162 | * after the given initial delay, and subsequently with the | ||
| 163 | * given delay between the termination of one execution and the | ||
| 164 | * commencement of the next. If any execution of the task | ||
| 165 | * encounters an exception, subsequent executions are suppressed. | ||
| 166 | * Otherwise, the task will only terminate via cancellation or | ||
| 167 | * termination of the executor. | ||
| 168 | * | ||
| 169 | * @param command the task to execute | ||
| 170 | * @param initialDelay the time to delay first execution | ||
| 171 | * @param delay the delay between the termination of one | ||
| 172 | * execution and the commencement of the next | ||
| 173 | * @param unit the time unit of the initialDelay and delay parameters | ||
| 174 | * @return a ScheduledFuture representing pending completion of | ||
| 175 | * the task, and whose <tt>get()</tt> method will throw an | ||
| 176 | * exception upon cancellation | ||
| 177 | * @throws RejectedExecutionException if the task cannot be | ||
| 178 | * scheduled for execution | ||
| 179 | * @throws NullPointerException if command is null | ||
| 180 | * @throws IllegalArgumentException if delay less than or equal to zero | ||
| 181 | */ | ||
| 182 | public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, | ||
| 183 | long initialDelay, | ||
| 184 | long delay, | ||
| 185 | TimeUnit unit); | ||
| 186 | |||
| 187 | } | ||