bounce2.java

里面包含了多个java的编程示例！而且举出初学者常常遇到的错误！

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

public class Bounce2 extends JFrame implements ActionListener {
    BouncePanel2 canvas;
    JTextField speed;
    
    public Bounce2() {
        super("Tennis");
        setSize(550, 450);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        BorderLayout border = new BorderLayout();
        setLayout(border);
        // set up animation panel
        canvas = new BouncePanel2();
        add(canvas, BorderLayout.CENTER);
        // set up speed panel
        JPanel speedPanel = new JPanel();
        JLabel speedLabel = new JLabel("Speed: ");
        speed = new JTextField("100", 10);
        JButton speedSetter = new JButton("Set");
        speedSetter.addActionListener(this);
        speedPanel.add(speedLabel);
        speedPanel.add(speed);
        speedPanel.add(speedSetter);
        add(speedPanel, BorderLayout.SOUTH);
        setVisible(true);
    }

    public static void main(String[] arguments) {
        Bounce2 af = new Bounce2();
    }
    
    // monitor the Set button
    public void actionPerformed(ActionEvent event) {
        try {
            int speedValue = Integer.parseInt(speed.getText());
            canvas.setDelay(speedValue);
        } catch (NumberFormatException exception) {
            // do nothing; invalid speed value
        }
    }
}