JAVA Thread Programming - New Runnable()

I'm very interested in Thread Programming. It will to be the parallel process, make all process done simultaneously in amount of times. It was also a hard coding and logic, because not another thread method can run smoothly. 

After I learned Java, it became realized, especially after I knew a new method Runnable(). Here is the example codes that implement the Thread and Runnable(). A Runnable() method will be posted and destroyed by an Handler(). Post method can be executed with a delay time.

In this codes, I use Android Studio with Java Programming. I created 2 threads that will execute 2 methods, display waiting timer (like stopwatch) and randomizing colors & numbers and then display it in Buttons.

I use join() function to make th2 will run after th1 executed completely. In this flow, th1 executes the reset procedure and th2 executes the counter process.

th1= new Thread(new Runnable() {

@Override
public void run() {
  bStopRun= true;
  handlerShow.removeCallbacks(timerShowNumber, 0);
  ResetBtn(btnChoices, 60, false);
}});
th1.start();


th2= new Thread(new Runnable() {

@Override
public void run() {
  try {
    th1.join();
  } catch (InterruptedException e) {
     e.printStackTrace();
  }

  bStopRun= false;
  mHandler.post(new Runnable() {
    @Override
    public void run() {
       StartTimeaAns = SystemClock.uptimeMillis();
       handlerShow.postDelayed(timerShowNumber, 0);
   }
 });

...
};
th2.start();

public Runnable timerShowNumber = new Runnable(){
  public void run(){
    if(bStopRun && bStopRunTh1){
      handlerShow.removeCallbacks(timerShowNumber);
      ResetToWhite();
      return;
    }
  MillisecondTimeAns = SystemClock.uptimeMillis() - StartTimeaAns;
...
}

This is the main codes of Sorting In Colors Apps.
Sorting In Colors Free Android App

Thank you...