8-1使用按钮选择绘制不同图形

编写一个程序，实现如下的界面，当点击不同按钮时绘制相应的图形。点击“椭圆”，绘制一个椭圆形；点击“矩形”，绘制一个矩形；点击“直线”，绘制一条直线。实现图形绘制即可，图形位置和大小自定。
参考代码

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Rectangle2D;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class b{public static void main(String[] args) {EventQueue.invokeLater(new Runnable() {public void run() {ChangeGraphFrame frame = new ChangeGraphFrame();frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setVisible(true);}});}
}
class ChangeGraphFrame extends JFrame {private GraphComponent graphComponent;public ChangeGraphFrame() {setSize(250, 200);setTitle("绘制图形");graphComponent = new GraphComponent();add(graphComponent, BorderLayout.CENTER);JButton elipseButton = new JButton("椭圆");elipseButton.addActionListener(new ChangeGraphAction(1));JButton rectButton = new JButton("矩形");rectButton.addActionListener(new ChangeGraphAction(2));JButton lineButton = new JButton("直线");lineButton.addActionListener(new ChangeGraphAction(3));JPanel buttonPanel = new JPanel();buttonPanel.add(elipseButton);buttonPanel.add(rectButton);buttonPanel.add(lineButton);add(buttonPanel, BorderLayout.SOUTH);
}
private class ChangeGraphAction implements ActionListener {private int choice;public ChangeGraphAction(int choice) {this.choice = choice;}public void actionPerformed(ActionEvent event) {graphComponent.setGraphChoice(choice);repaint();}}
}class GraphComponent extends JComponent {private int graphChoice = 0;public int getGraphChoice() {return graphChoice;}public void setGraphChoice(int graphChoice) {this.graphChoice = graphChoice;}public void paintComponent(Graphics g) {Graphics2D g2 = (Graphics2D) g;Ellipse2D elipse = new Ellipse2D.Double(70, 10, 100, 100);Rectangle2D rect = new Rectangle2D.Double(70, 10, 100, 100);Line2D line = new Line2D.Double(10, 10, 200, 100);switch (graphChoice) {case 1:g2.draw(elipse);break;case 2:g2.draw(rect);break;case 3:g2.draw(line);break;}}
}