How to break if field is empty

   private void loginActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String Username=username.getText().toString();
        String PassWord=password.getText().toString();

         if(Username.equals("")){ 
             JOptionPane.showMessageDialog(null,"User name is mandatory");
        }
          if(PassWord.equals("")){
              JOptionPane.showMessageDialog(null,"Password is mandatory");
          }

          }

          addJobOpenning second= new addJobOpenning();
          second.setVisible(true);