Data validation for preventing blank entries
Extract the input code into a method:

String getNonBlankInput(String prompt) {
   String input = JOptionPane.showInputDialog(prompt);

   while (input.equals("")) {
      JOptionPane.showMessageDialog(null, "Cannot accept blank entries!");
      input = JOptionPane.showInputDialog(prompt);
   }

   return input;
}


Usage:

String name = getNonBlankInput("Enter name: ");