java题目该如何做

java题目该怎么做？
编写一个Applet程序，在程序中包含一个滚动条，在Applet程序中绘制一个圆，用滚动条滑块显示的数字表示该圆的直径，当用户拖动滑块时，圆的大小随之改变。




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作业题
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这个还不简单？
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import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JApplet;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class Applet1 extends JApplet {
private JPanel jpanel;
private JSlider jslider;
private Container contentPane = getContentPane();

public void init() {
jpanel = new JPanel();
jslider = new JSlider(50, 100);
jslider.putClientProperty( "JSlider.isFilled ", Boolean.TRUE);
jslider.setPaintLabels(true);
jslider.setMajorTickSpacing(10);

GridBagLayout gbl = new GridBagLayout();
GridBagConstraints constraints = new GridBagConstraints();

jpanel.setLayout(gbl);
constraints.gridx = 4;
constraints.gridy = 0;
constraints.gridwidth = 1;
constraints.gridheight = 1;
constraints.weightx = 4;
constraints.weighty = 1;
constraints.fill = GridBagConstraints.NONE;
gbl.setConstraints(jslider, constraints);
jpanel.add(jslider);

contentPane.setLayout(new BorderLayout());
contentPane.add( "Center ", jpanel);
final CircleCanvas kc = new CircleCanvas(jslider);
contentPane.add( "South ", kc);
jslider.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
kc.setRadius(jslider.getValue());
kc.repaint();
}
});
}
}

class CircleCanvas extends Canvas {
private JSlider js;
private int diameter;

public CircleCanvas(JSlider js) {
this.js = js;
setSize(170, 120);
}

public void paint(Graphics g) {
diameter = js.getValue();
g.setColor(Color.red);
g.drawOval(40, 10, diameter, diameter);
}

public void setRadius(int radius){
this.diameter = radius;
}
}