title: How can I check if two JTextfields are empty and display a JOptionpane if they are?
body: <p>Below is the method that I need to add the code to. It should check to see if the Jtextfields are empty and show a JOptionpane if they are. if not, it should call the calculateSubtotal method</p>
  
  <pre><code>private void calculateBillJButtonActionPerformed(    
    ActionEvent event )   
  </code></pre>
  
  <p>{<br>
        double total = calculateSubtotal();   </p>
  
  <pre><code>  // display subtotal, tax and total   
    displayTotal( total );   
  </code></pre>
  
  <p>} // end method calculateBillJButtonActionPerformed</p>