Java How to Program, Early Objects, 11th Edition

... JOptionPane.PLAIN_MESSAGE);
49         }
50      }
51
52      // retrieve equation from web service and display left side to user
53      private void generateJButtonActionPerformed(
54         java.awt.event.ActionEvent evt)
55      {
56         try
57         {
58            String url = String.format("http://localhost:8080/" + 
59               "EquationGeneratorXML/webresources/equation/%s/%d",
60               operation, difficulty);                            
61
62            // convert XML back to an Equation object
63            Equation equation = JAXB.unmarshal(url, Equation.class); 
64
65            answer = equation.getResult();                             
66            equationJLabel.setText(equation.getLeftHandSide() + " ="); 
67            checkAnswerJButton.setEnabled(true);
68         }
69         catch (Exception exception)
70         {
71            exception.printStackTrace();
72         }
73      }
74
75      // obtains the mathematical operation selected by the user
76      private void operationJComboBoxItemStateChanged( ...