Question

Not sure I understand threads correctly, could someone tell me whether I´m right or wrong in the following example:

class Task {
String taskName;
private Thread thread;
boolean isFinished;

public Task(String name){
    taskName = name;
}

public void createTask(final Runnable r) {
    thread = new Thread(r){
        public void run(){
            if(r != null) {
                r.run();
                isFinished = true;
            }
        }
    };
    thread.start();
}
}

What I’m actually doing in my app is that I set the isFinished to true, and have an observer that whenever the isFinished is true does some stuff. I’m afraid that isFinished is set to true, before all code in the Runnable I pass as parameter is actually terminated.

Isn’t the run method suppose to put the code I pass, in a separate thread and run that code asynchronously?

Answer 1

The way you wrote your code, isFinished will not be set to true until r.run() is complete. It may be appearing otherwise because you may have some data visibility issues due to missing synchronization or missing volatile declarations.

It’s a little bit odd since you’re both passing in the Runnable to the constructor, but calling it using the reference from your method declaration, not the one inside the thread. But it “works”, there’s just a redundancy there.

As an aside, don’t forget @Override in your anonymous class 🙂