title: How to avoid generating the same 2 random numbers twice in a row
body: <p>I am trying to set the background color of a view using a timer to change the color every few seconds, but often a color is set twice in a row due to the fact that the random number referring to a specific color is generated twice. How can I change the code to avoid generating the same random number twice in a row?</p>
  
  <pre><code>final Runnable runnable = new Runnable() {
  
      @Override
      public void run() {
  
          Random rand = new Random();
          int n = rand.nextInt(3);
          n += 1;
  
  
          switch (n){
  
              case 1:
  
                  colorView.setBackgroundColor(Color.GREEN);
                  break;
  
              case 2:
  
                  colorView.setBackgroundColor(Color.MAGENTA);
                  break;
  
              case 3:
  
                  colorView.setBackgroundColor(Color.CYAN);
                  break;
  
          }
  
      }
  };
  </code></pre>