Calling Runnable's run() method directly on thread object [duplicate]

Question

We cannot call Runnable's run() method directly on thread's object but according to the below program we are doing it without any compilation or Runtime errors. Why is it so?

public class ThreadCheck implements Runnable {

    @Override
    public void run() {
        for (int i=0; i<10; ) {
            System.out.println(++i);
        }
    }

    public static void main(String[] args) {
        Thread mythread = new Thread(new ThreadCheck());
        mythread.run();
        mythread.run();
        mythread.start();
    }   
}

Output: 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

Answer 1

This will not have any compilation or run-time errors. But it also will not spawn new threads. It will execute the run() method in the current main thread.

refer what will happen if we directly call run method?

Answer 2

We can call Runnable's run() method directly on thread's object. But, when you call run() method from thread's object, the run() method will work as a normal method. When you call it, it doesn't create a new thread.

In this case the run() method will be treated as a normal method call. But when you call the start() method on the Thread object, then it automatically calls the run() method on a new thread in the JVM.