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POThreadPoolExecutor Utility methods
 

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  1. POThreadPoolExecutor Utility methods
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    <p>I am writing a thread pool utility in my <code>multithreading</code> program. i just need to validate the following methods are correct and are they return the right values for me. i am using a <code>LinkedBlockingQueue</code> with size of 1. and also I refer to the java doc and it always says 'method will return <strong>approximate</strong>' number phrase. so i doubt weather following conditions are correct.</p> <pre><code>public boolean isPoolIdle() { return myThreadPool.getActiveCount() == 0; } public int getAcceptableTaskCount() { //initially poolSize is 0 ( after pool executes something it started to change ) if (myThreadPool.getPoolSize() == 0) { return myThreadPool.getCorePoolSize() - myThreadPool.getActiveCount(); } return myThreadPool.getPoolSize() - myThreadPool.getActiveCount(); } public boolean isPoolReadyToAcceptTasks(){ return myThreadPool.getActiveCount()&lt;myThreadPool.getCorePoolSize(); } </code></pre> <p>Please let me know your thoughts and suggestions.</p> <p>UPDATE </p> <p>interesting thing was if pool returns me there are 3 threads available from the <code>getAcceptableTaskCount</code> method and when i pass 3 tasks to the pool some times one task got rejected and it is handle by <code>RejectedExecutionHandler</code>. some times pool will handle all the tasks i passed. i am wondering why pool is rejected the tasks since i am passing tasks according to the available thread count. </p> <p>--------- implementation of the answer of gray---</p> <pre><code>class MyTask implements Runnable { @Override public void run() { try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("exec"); } </code></pre> <p>}</p> <pre><code>@Test public void testTPool(){ ExecutorService pool = Executors.newFixedThreadPool(5); List&lt;Future&lt;MyTask&gt;&gt; list = new ArrayList&lt;Future&lt;MyTask&gt;&gt;(); for (int i = 0; i &lt; 5; i++) { MyTask t = new MyTask(); list.add(pool.submit(t, t)); } for (int i = 0; i &lt; list.size(); i++) { Future&lt;MyTask&gt; t = list.get(i); System.out.println("Result -"+t.isDone()); MyTask m = new MyTask(); list.add(pool.submit(m,m)); } } </code></pre> <p>This will print <code>Result -false</code> in the console meaning that task is not complete.</p>
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    1. USSam
    1. USSam
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    1. COCan you explain _why_ you want to get this information? As the documentation states, there are race conditions around getting those statistics so your methods are going to be subject to them as well. They will be returning approximations.
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      1. USGray
    2. CO@Gray - fist i want to do some file processing in my application. for that i scheduled a job. so once job is wake up and try to send tasks to the pool ,i need to know that if pool is idle or pool can accept the tasks. if pool can accept, i need to know how much free threads in the pool. if it is 5 i will send 5 tasks to the pool to do the processing.
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      1. USSam
    3. COYou would be better off limiting the tasks rather than the threads. Trying to micro-manage threads, or thread pools, is difficult and error/disaster-prone. Typically, I throttle such designs by object pooling. If I create 16 tasks at startup, store them on a producer-consumer 'pool queue' and arrange that every thread that wants to issue a task to the threadpool has to get one from the poolQueue, that limits the number of tasks running at any one time to 16 without dodgy 'getState' threadpool calls. The threadpool can requeue the tasks, when done, so that they can be recycled.
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      1. USMartin James
 

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