ExecutorService Runnable/Callable

Runnable:no return
Callable:return
Future interface#get methodでreturnを取得する

public class Outer {
    public static void main(String[] args) throws InterruptedException {
        ExecutorService e = Executors.newSingleThreadExecutor();
        Runnable r = () -> {
            System.out.println("runnable");
        };
        Callable<Integer> c = () -> {
            return 1;
        };
        Future f = e.submit(r);
        try {
            System.out.println(f.get());
        } catch (ExecutionException ex) {
            Logger.getLogger(Outer.class.getName()).log(Level.SEVERE, null, ex);
        }
        Future<Integer> f2 = e.submit(r,0);
        try {
            System.out.println(f2.get());
        } catch (ExecutionException ex) {
            Logger.getLogger(Outer.class.getName()).log(Level.SEVERE, null, ex);
        }
        f2 = e.submit(c);
        try {
            System.out.println(f2.get());
        } catch (ExecutionException ex) {
            Logger.getLogger(Outer.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

runnable
null
runnable
0
1