How to make a plain old class run a method in a separate Thread?

in other words: a class that neither extends Thread nor implements Runnable!

Here is the example I have..
public class Main {
    public static void main(String[] args) {
        final Counter counter = new Counter();
        counter.countInOwnThread();
        ThreadSleeper.sleepMillisIgnoreInterrupt(200);
        System.out.println("Hello from main thread..!");
    }
}
 
class Counter {
 
    public void count() {
        for (int i = 0; i < 10; i++) {
            ThreadSleeper.sleepMillisIgnoreInterrupt(50);
            System.out.println("I am running..");
        }                    
    }
 
    public void countInOwnThread() {
        final Runnable runnable = new Runnable() {
            @Override 
            public void run() {
                count();
            }
        };
        new Thread(runnable).start();
    }
}
 
class ThreadSleeper {
    public static void sleepMillisIgnoreInterrupt(final int millis) {
        try {
            Thread.sleep(millis);    
        } catch (InterruptedException e) {
            // ignore!
        }        
    }
}