Question

I would like to create a worker thread that should be shared within other sessions. Basically I want to restrict other users from doing the same process. So They will retrieve the thread via a static Instance of object thread that I created. If the thread is still alive, then they will be prompted with error.

Is there a other way to do this because I am thinking if placing a Thread object within a static is safe? I am also thinking of application context but I am not sure which is better way to do this in java?

Answer 1

Placing any object in a static or in any kind of shared location is not intrinsically unsafe but you need to take care with the design.

declare

  static Thing t;

initialise

  if ( t == null ) {
       t = new Thing();
  } 

use

t.dosomething();

Now what happens if two threads hit the initialise block at the same time? You can get two Things created. Probably don’t want that, so use synchronisation.

synchronized void intialise() {
    if ( t == null ) {
       t = new Thing();
  } 

}

what happens if two threads attempt to use the t at the same time. This depends on the promises made by Thing. If it’s thread-safe no problem, otherwise your code needs to provide synchronisation

  synchronized void doSomthing() {
        t.doSomething();
  }