How to use TimerTask with lambdas?

Question

As you hopefully know you can use lambdas in Java 8, for example to replace anonymous methods.

An example can be seen here of Java 7 vs Java 8:

Runna         


        

Answer 1

To complete Marko Topolnik's answer about Timer, you just have to call schedule method with a lambda.

schedule(() -> {
    System.out.println("Task #1 is running");
}, 500);

Answer 2

Noting first that Timer is effectively an antiquated API, but entertaining your question nevertheless, you could write a small wrapper around it which would adapt the schedule method to accept a Runnable, and on the inside you'd turn that Runnable into a TimerTask. Then you would have your schedule method which would accept a lambda.

public class MyTimer {
  private final Timer t = new Timer();

  public TimerTask schedule(final Runnable r, long delay) {
     final TimerTask task = new TimerTask() { public void run() { r.run(); }};
     t.schedule(task, delay);
     return task;
  }
}

Answer 3

While Marko's answer is perfectly correct, I prefer my implementation:

public class FunctionalTimerTask extends TimerTask {

    Runnable task;

    public FunctionalTimerTask(Runnable task) {
        this.task = task;
    }

    @Override
    public void run() {
        task.run();
    }
}

 public static class Task {
    public static TimerTask set(Runnable run) {
        return new FunctionalTimerTask(() -> System.err.println("task"));
    }
}

 Timer timer = new Timer(false);
 timer.schedule(Task.set(() -> doStuff()), TimeUnit.SECONDS.toMillis(1));

This gives you more control over the timer, and you have a static utility class. Idealy give it a name that won't conflict with other common thread class, so not Task, Job, Timer.

Answer 4

I know this is an old post, but for completeness, I wanted to include the wrapper solution posted by Flown:

private static TimerTask wrap(Runnable r) {
  return new TimerTask() {

    @Override
    public void run() {
      r.run();
    }
  };
}

then your call can become:

timer.schedule(wrap(this::checkDirectory), delay);

Answer 5

You can also create a Timer easily with lambdas from the Swing API if you want (but not with TimerTask) :

new javax.swing.Timer(1000, (ae) -> this::checkDirectory).start();