Create a simple queue with Java threads

Question

I\'m trying to create a simple queue with Java Thread that would allow a loop, say a for loop with 10 iterations, to iterate n (< 10) threads at a time and wait until tho

Answer 1

Use the Executors, as recommended by the others. However, if you want the fun of doing it yourself, try something like this. (Take care. I wrote it in Notepad and there's some Exceptions you'll need to catch even if I got everything else right. Notepad's poor at catching coding errors.) This is more a concept than an actual solution to anything, but the idea could be generally useful.

private ConcurrentLinkedQueue  tQueue =
             new ConcurrentLinkedQueue();

class MyThread  extends Thread  {
    public Runnable  doSomething;

    public void run()  {
        // Do the real work.
        doSomething();
        // Clean up and make MyThread available again.
        tQueue.add( mythread );
        // Might be able to avoid this synch with clever code.
        // (Don't synch if you know no one's waiting.)
        // (But do that later.  Much later.)
        synchronized (tQueue)  {
            // Tell them the queue is no longer empty.
            tQueue.notifyAll();
        }
    }
}

Elsewhere:

// Put ten MyThreads in tQueue.
for (int i = 0; i < 10; i++)  tQueue.add( new MyThread() );

// Main Loop.  Runs ten threads endlessly.
for (;;)  {
    MyThread  t = tQueue.poll();
    if (t == null)  {
        // Queue empty.  Sleep till someone tells us it's not.
        do  {
            // There's a try-catch combo missing here.
            synchonized( tQueue )  { tQueue.wait() };
            t = tQueue.poll();
        }  while (t == null)  break;  // Watch for fake alert!
    }
    t.doSomething = do_some_work;
    t.start();
}

Also, note the clever use of ConcurrentLinkedQueue. You could use something else like ArrayList or LinkedList, but you'd need to synchronize them.