本题是一个Applet,功能是用鼠标画不同颜色的图形。页面中有5个按钮“画红色图形”、“画绿色图形”、“画蓝色图形”、“橡皮”和“清除”,单击前三个按钮中的一个,按住鼠标左键或右键在面板中拖动,就能两出对应颜色的线条,单击“橡皮”按钮,按住鼠标左键或右键在面板中拖动就能将面板中的图形擦除掉,单击“清除”按钮,就能将面板中所有的图形清除掉。 import java.applet.*; import java.awt.*; import java.awt.event.*; public class java3 extends Applet implements ActionListener {int x=-1,y=-1,rubberNote=0,clearNote=0; Color C=new Color(255,0,O); int con=3; Button b_red,b_blue,b_green,b_clear,b_quit; public void init() { addMouseMotionListener(this); b_red=new Button('画红色图形'); b_blue=new Button('画蓝色图形'); b_green=new Button('画绿色图形'); b_quit=new Button('橡皮'); b_clear=new Button('清除'); add(b_red); add(b_green); add(b_blue); add(b_quit); add(b_clear); b_red.addActionListener(this); b_green.addActionListener(this); b_blue.addActionListener(this); b_quit.addActionListener(this); b_dear.addActionListener(this); } public void paint() (if(x!=-l&&y!=-l&rubberNote= = 0R&;clearNote= =0) {g.setColor(c); g.filloval(X,Y,con,con); } else if(rubberNote= =1&;&;clearNote= =O) {g.clearRect(x,Y,10,10); } else if(clearNote= =1&;&;rubberNote= =O) {g.clearRect(0,0,getSize().width,getSize(). height); } } public void mouseDragged(MouseEvent e) {x=(int)e.getX();y=(int)e.getY();repaint(); } public void mouseMoved(MouseEvent e){) public void update(Graphics g) {paint(g); } public void actionPerformed(Event e) {if(e.getSource()= =b-red) {rubberNote=0;clearNote=0;c=new Color (255,0,0); } else if(e.getSource()= =b_green) {rubberNore=0;clearNote=0;C=new Color(0, 255,0); } else if(e.getSource()= =b_blue) {rubberNote=0;clearNote=0;C=new Color(0, 0,255); } if(e.getSource()= =b—quit) {rubberNote=1;clearNote=0; } if(e.getSource()= =b—clear) {clearNote=1;rubberNote=0;repaint(); } } }