I have some jobs running to start periodically some business process, but I want to be able to stop these jobs before their end without killing the thread to be able to finish some other process after.

So I have a boolean isInterrupted in my JobRunner, which is set at true when I want to interrupt the job.

My Job is calling a service method, and this method is basically a big for each (just to mention that this process should stay here and not be moved to the job). I want to stop this for when the isInterrupted variable is true.

Is there any way to pass this value by reference, or to pass a getter function as parameter as we could do in Javascript?

For information we are using in Java 8

CodePudding user response：

You can pass a BooleanSupplier.

class Finisher {
  private volatile boolean finished = false;
  public boolean isFinished() { return finished; }
}
class Runner {
  public void run(BooleanSupplier finishedSupplier) {
    while (!finishedSupplier.getAsBoolean()) {
      // do work
    }
  }

  public static void main() {
    Runner runner = new Runner()
    Finisher finisher = new Finisher();
    runner.run(finisher::isFinished);
  }
}

Of course, the finisher instance must somehow be able to update its finished flag. The code here is just for illustrative purposes to show how the syntax would be used.

finisher::isFinished is a method reference and is (more or less) equivalent to writing () -> finisher.isFinished().

CodePudding user response：

If you want to pass a reference to some external boolean that may change over time, there are two main ways to do it:

1. Pass an AtomicBoolean. Changes to its internal value in one thread can be seen in another thread.
2. Pass a Supplier<Boolean> to the child thread, which is effectively a metod reference to some method that returns a Boolean.

Edit: As pointed out by knittl, Java also has a BooleanSupplier that returns a boolean instead of a Boolean. In this case, that would presumably be preferable.