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copied!<p>A scheduled task is either being executed or is waiting to be executed. </p> <p>If the task is waiting to be executed, <code>future.cancel()</code> will prevent it from being executed (both cancel(true)/cancel(false)). </p> <p>If the task is already being executed, <code>future.cancel(false)</code> will have no effect. <code>future.cancel(true)</code> will interrupt the thread that is executing that task. <strong>Whether this will have any effect is up to you</strong>, who will implement that task. A task may or may not respond to interruption depending on the implementation. </p> <p>In order to make your task responsive to cancellation, you must implement <code>doSomething()</code> so that it will respond to interruption. </p> <p>There are basically two way to do this:</p> <p>1.Check interruption flag in your logic</p> <pre><code>public void doSomething(){ stuff(); //Don't use Thread.interrupt() if(Thread.currentThread().isInterrupted()){ // We have an interruption request, possibly a cancel request //Stop doing what you are doing and terminate. return; } doLongRunningStuff(); } </code></pre> <p>You must occasionally check for the interruption flag, and if interrupted, stop what you are doing and return. Be sure to use Thread.isInterrupted() and not Thread.interrupt() for the check.</p> <p>2.Act upon Interrupted exception</p> <pre><code>public void doSomething(){ try{ stuff(); }catch(InterruptedException e){ // We have an interruption request, possibly a cancel request // First, preserve Interrupted Status because InterruptedException clears the // interrupted flag Thread.currentThread.interrupt(); // Now stop doing your task and terminate return; } doLongRunningStuff(); } </code></pre> <p>When you have any method that throws InterruptedException, be sure to stop what you doing and terminate when one is thrown. </p> <p>Once you implement your methods in this way, you can call future.cancel(true) to cancel the execution of a running task.</p>

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