accountapplet.java

此源码为机械工业出版社出版的《Java语言程序设计》第三版所配套的书中所有源代码。

// AccountApplet.java: Use custom exception classes
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;

public class AccountApplet extends JApplet implements ActionListener
{
  // Declare text fields
  private JTextField jtfID, jtfBalance, jtfDeposit, jtfWithdraw;

  // Declare Deposit and Withdraw buttons
  private JButton jbtDeposit, jbtWithdraw;

  // Create an account with initial balance $1000
  private Account account = new Account(1, 1000);

  // Create a label for showing status
  private JLabel jlblStatus = new JLabel();

  // Initialize the applet
  public void init()
  {
    // Panel p1 to group ID and Balance labels and text fields
    JPanel p1 = new JPanel();
    p1.setLayout(new GridLayout(2, 2));
    p1.add(new JLabel("Accout ID"));
    p1.add(jtfID = new JTextField(4));
    p1.add(new JLabel("Account Balance"));
    p1.add(jtfBalance = new JTextField(4));
    jtfID.setEditable(false);
    jtfBalance.setEditable(false);
    p1.setBorder(new TitledBorder("Display Account Information"));

    // Panel p2 to group deposit amount and Deposit button and
    // withdraw amount and Withdraw button
    JPanel p2 = new JPanel();
    p2.setLayout(new GridLayout(2, 3));
    p2.add(new JLabel("Deposit"));
    p2.add(jtfDeposit = new JTextField(4));
    p2.add(jbtDeposit = new JButton("Deposit"));
    p2.add(new JLabel("Withdraw"));
    p2.add(jtfWithdraw = new JTextField(4));
    p2.add(jbtWithdraw = new JButton("Withdraw"));
    p2.setBorder(new TitledBorder("Deposit or withdraw funds"));

    // Place panels p1, p2, and label in the applet
    this.getContentPane().add(p1, BorderLayout.WEST);
    this.getContentPane().add(p2, BorderLayout.CENTER);
    this.getContentPane().add(jlblStatus, BorderLayout.SOUTH);

    // Refresh ID and Balance fields
    refreshFields();

    // Register listener
    jbtDeposit.addActionListener(this);
    jbtWithdraw.addActionListener(this);
  }

  // Handle ActionEvent
  public void actionPerformed(ActionEvent evt)
  {
    String actionCommand = evt.getActionCommand();
    if (evt.getSource() instanceof JButton)
      if ("Deposit".equals(actionCommand))
      {
        try
        {
          double depositValue = (Double.valueOf(
            jtfDeposit.getText().trim())).doubleValue();
          account.deposit(depositValue);
          refreshFields();
          jlblStatus.setText("Transaction Processed");
        }
        catch (NegativeAmountException ex)
        {
          jlblStatus.setText("Negative Amount");
        }
      }
      else if ("Withdraw".equals(actionCommand))
      {
        try
        {
          double withdrawValue = (Double.valueOf(
            jtfWithdraw.getText().trim())).doubleValue();
          account.withdraw(withdrawValue);
          refreshFields();
          jlblStatus.setText("Transaction Processed");
        }
        catch(NegativeAmountException ex)
        {
          jlblStatus.setText("Negative Amount");
        }
        catch (InsufficientFundException ex)
        {
          jlblStatus.setText("Insufficient Funds");
        }
      }
  }

  // Update the display for account balance
  public void refreshFields()
  {
    jtfID.setText(String.valueOf(account.getId()));
    jtfBalance.setText(String.valueOf(account.getBalance()));
  }
}