How to make Jlabel visible and invisible using for loop in java?

I have the following code. I want to Make jLabel Visible and Invisible 4 times with 0.5Seconds delay for every loop. The code below is not working as expected.

String a = (String)jTextField1.getText();

  if(a.equals("")){

  for (int i = 0;i<=3;i++){
      try {
         jLabel1.setVisible(true);
          Thread.sleep(500);


          for(int j=0;j<i;j++){
          jLabel1.setVisible(false);
           Thread.sleep(500);
          }

      } catch (InterruptedException ex) {

      }
  }
  }