Re: [Threading to manage simulated printing jobs]

Lew <>
Sun, 09 Sep 2007 14:33:39 -0400
<> wrote:

Hello to all Javascript programmers out there. :)

Wrong group. They won't be listening here.

I am really ashamed to say that even after 6 months of intermittent
Java programming I have been a complete failure at grasping the
concepts or the real thing behind 'threading'.

Join the crowd. Nearly all Java programmers have yet to grok threading.

class Consumer {
    private static int gId;

Accessed by many threads, yet you don't synchronize those accesses. Not safe.

Do not use TAB characters in Usenet posts.

  private PrintQueue queue;

  private String id;

  private Consumer() {

You do not need this constructor. Also, it's conventional to place all
constructor definitions together.

  private Runnable job = new Runnable() {
    public void run() {
      // start consuming the print jobs and print them
      try {
        for (;;) {
          //System.out.println("Inside run of producer");

Use logging, not System.out.println(). And isn't this the consumer?

          PrintJob job = queue.getJob();

You'd better make sure the queue is synchronized!

          if (job != null)
            System.out.println(id + job.print());

Use logging, not System.out.println(). And you forgot your braces.

      } catch (Exception e) {

  public Consumer(PrintQueue queue) throws Exception {
    this.queue = queue; = "Consumer" + gId;


    Thread t = new Thread(job);
    t.join(); /* Does this even do anything? */

Have you read the Javadocs on Thread.join?
It causes the current thread to wait for the target thread to finish. Of
course, in your case it hasn't started yet.


I am thinking it's a bad idea to fire off threads or do any significant work
in the constructor.


Buy and study /Java Concurrency in Practice/ by Brian Goetz, et al.


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