The java interface ExecutorService has several submit methods which accept Runnable or Callable task as parameter. Can I pass an object method?

Question

The interface java.util.concurrent.ExecutorService has several submit methods, The second one accept a Runnable task parameter. However, I saw some code like this, first is the Counter class:

public class Counter {
    private int count;
    public void increment() {
        count++;
    }
    public int getCount() {
        return count;
    }
}

and the Demo class:

public class Demo {
    private Counter counter = new Counter();
    public void demoCounter() {
        ExecutorService service = Executors.newCachedThreadPool();
        IntStream.range(0, 1000)
            forEach(i -> service.submit(counter:: increment));
        service.shutdown();
        System.out.println("Counter count=" + counter.getCount());
    }
    public void main(String[] args) {
        Demo demo = new Demo();
        demo.demoCounter();
    }
}

What I wonder is that in the Demo class, the submit method's parameter is counter:: increment which I think is not a Runnable task Object. So, was there something magic happened?

https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html — JB Nizet, Jun 25 '17 at 09:23
And this: https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html#target-typing — Seelenvirtuose, Jun 25 '17 at 09:25
But note that this code example is broken as the `increment()` method is not thread safe and this code lets multiple threads call it the on the same object. — Holger, Jul 12 '17 at 08:46

The java interface ExecutorService has several submit methods which accept Runnable or Callable task as parameter. Can I pass an object method?

0 Answers0