ThreadOrRunnable?

Subclass or Runnable?

There are no rules about which of the two methods that is the best. Both methods works. Personally though, I prefer implementing Runnable, and handing an instance of the implementation to a Thread instance. When having the Runnable's executed by a thread pool it is easy to queue up the Runnable instances until a thread from the pool is idle. This is a little harder to do with Thread subclasses.

Sometimes you may have to implement Runnable as well as subclass Thread. For instance, if creating a subclass of Thread that can execute more than one Runnable. This is typically the case when implementing a thread pool.

public class ThreadExample {
	
  public static void main(String[] args){
    System.out.println(Thread.currentThread().getName());
    for(int i=0; i<10; i++){
      new Thread("" + i){
        public void run(){
          System.out.println("Thread: " + getName() + " running");
        }
      }.start();
    }
  }
}

Note that even if the threads are started in sequence (1, 2, 3 etc.) they may not execute sequentially, meaning thread 1 may not be the first thread to write its name to System.out. This is because the threads are in principle executing in parallel and not sequentially. The JVM and/or operating system determines the order in which the threads are executed. This order does not have to be the same order in which they were started.