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Monday, 6 March 2017

Chapter 32 Exercise 4, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

32.4 (Find grades) Listing 32.2, FindGrade.java, presented a program that finds a student’s grade for a specified course. Rewrite the program to find all the grades for a specified student, as shown in Figure 32.29.


import javax.swing.*;
import java.sql.*;
import java.awt.*;
import java.awt.event.*;

public class Exercise04 extends JApplet {
 private static final long serialVersionUID = 1L;
 private JTextField jtfSSN = new JTextField(9);
 private JButton jbtShowGrade = new JButton("Show Grade");
 private JTextArea jTextArea = new JTextArea();
 
 // PreparedStatement for executing queries
 private PreparedStatement preparedStatement;

 /** Initialize the applet */
 public void init() {
  // Initialize database connection and create a Statement object
  initializeDB();

  jbtShowGrade.addActionListener(new ActionListener() {
   @Override
   public void actionPerformed(ActionEvent e) {
    jbtShowGrade_actionPerformed(e);
   }
  });

  JPanel jPanel1 = new JPanel();
  jPanel1.add(new JLabel("SSN"));
  jPanel1.add(jtfSSN);
  jPanel1.add(jbtShowGrade);

  add(jPanel1, BorderLayout.NORTH);
  jTextArea.setEditable(false);
  add(jTextArea, BorderLayout.CENTER);
  
  
 }

 private void initializeDB() {
  try {
   Class.forName("com.mysql.jdbc.Driver");
   System.out.println("Driver loaded");
   Connection connection = DriverManager.getConnection("jdbc:mysql://localhost/javabook", "root", "root");
   System.out.println("Database connected");
   String queryString = "select firstName, mi, lastName, title, grade from Student, Enrollment, Course where Student.ssn = ? and Enrollment.ssn = Student.ssn and Enrollment.courseId = Course.courseId";
   preparedStatement = connection.prepareStatement(queryString);
  } catch (Exception ex) {
   ex.printStackTrace();
  }
 }

 private void jbtShowGrade_actionPerformed(ActionEvent e) {
  String ssn = jtfSSN.getText();
  try {
   preparedStatement.setString(1, ssn);
   ResultSet rset = preparedStatement.executeQuery();

   jTextArea.setText("");
   while (rset.next()) {
    String lastName = rset.getString(1);
    String mi = rset.getString(2);
    String firstName = rset.getString(3);
    String title = rset.getString(4);
    String grade = rset.getString(5);

    jTextArea.append(firstName + " " + mi + " " + lastName + "'s grade on course " + title + " is " + grade + "\n");
   }
  } catch (SQLException ex) {
   ex.printStackTrace();
  }
 }

 /** Main method */
 public static void main(String[] args) {
  Exercise04 applet = new Exercise04();
  JFrame frame = new JFrame();
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.setTitle("Exercise04");
  frame.getContentPane().add(applet, BorderLayout.CENTER);
  applet.init();
  applet.start();
  frame.setSize(400, 400);
  frame.setLocationRelativeTo(null); // Center the frame
  frame.setVisible(true);
 }
}

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