显示一个字符

（显示一个字符）编写一个程序，从键盘获得一个字符输入，并且将该字符显示在鼠标点击的位置import java.awt.*;import java.awt.event.*;import javax.swing.*;publicclass Exercise14_8extends JFrame {private panel = new DisplayPanel();public Exercise14_8() {getContentPane().add(panel, BorderLayout.CENTER);panel.setFocusable(true);}/** Main method */publicstaticvoid main(String[] args) {JFrame frame = new Exercise14_8();frame.setTitle("Exercise14_8");frame.setSize(300, 300);frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setVisible(true);}class DisplayPanel extends JPanelimplements KeyListener, MouseMotionListener {privateint x = 20;privateint y = 20;privatechar keyChar = ' '; // Default keypublic DisplayPanel() {this.addKeyListener(this); // Add listenerthis.addMouseMotionListener(this); // Add mouse motion listener }publicvoid mouseMoved(MouseEvent e) {x = e.getX();y = e.getY();}publicvoid mouseDragged(MouseEvent e) {}publicvoid keyReleased(KeyEvent e) {}publicvoid keyTyped(KeyEvent e) {}publicvoid keyPressed(KeyEvent e) {keyChar = e.getKeyChar();repaint();}publicvoid paintComponent(Graphics g) {super.paintComponent(g);g.setFont(new Font("TimesRoman", Font.PLAIN, 24));g.drawString(String.valueOf(keyChar), x, y);}}}用java编程，实现一个自己的记事簿程序。

要求：不用菜单，而用2个按钮，一个用来“打开文件”，另一个用来“保存文件”。

文本编辑框可用JTextArea组件。

import java.awt.*;import javax.swing.*;import java.awt.event.*;import javax.swing.event.*;import java.util.*;publicclass NotePad extends JFrame{JTextArea jta;class openl implements ActionListener{ publicvoid actionPerformed(ActionEvent e){JFileChooserjf=new JFileChooser();jf.showOpenDialog(NotePad.this);}}//保存文件的监听class savel implements ActionListener{publicvoid actionPerformed(ActionEvent e){JFileChooserjf = new JFileChooser();jf.showSaveDialog(NotePad.this);}}//构造函数public NotePad(){jta=new JTextArea("",24,40);JScrollPanejsp=new JScrollPane(jta);JMenuBarjmb=new JMenuBar();JButtonmOpen=new JButton("打开文件");mOpen.addActionListener(new openl());JButtonmSave=new JButton("保存文件");mSave.addActionListener(new savel());jmb.add(mOpen);jmb.add(mSave);this.setJMenuBar(jmb);this.getContentPane().add(jsp);this.setSize(200,200);this.setVisible(true);}//主函数，程序入口点publicstaticvoid main(String s[]){new NotePad();}}跳动的小球import javax.swing.Timer;import java.awt.*;import javax.swing.*;import java.awt.event.*;publicclass Ball extends JPanel{privateint delay = 10;protected Timer timer = new Timer(delay,new TimerListener());privateint x = 0;privateint y = 0;privateint radius = 5;privateint dx = 2;privateint dy = 2;public Ball(){timer.start();}privateclass TimerListener implements ActionListener{publicvoid actionPerformed(ActionEvent e){repaint();}}protectedvoid paintComponent(Graphics g){super.paintComponent(g);g.setColor(Color.red);if(x<radius) dx=Math.abs(dx);if(x>getWidth()-radius) dx=-Math.abs(dx);if(y<radius) dy=Math.abs(dy);if(y>getWidth()-radius) dy=-Math.abs(dy);x = x+dx;y = y+dy;g.fillOval(x-radius,y-radius,radius*2,radius*2);}publicvoid suspend(){timer.stop();}publicvoid resume(){timer.start();}publicvoid setDelay(int delay){this.delay=delay;timer.setDelay(delay);}}import java.awt.*;import javax.swing.*;import java.awt.event.*;publicclass BallControl extends JPanel{private Ball ball = new Ball();private JButton jbtSuspend =new JButton("Suspend");private JButton jbtResume =new JButton("Resume");private JScrollBar jsbDelay = new JScrollBar();public BallControl(){JPanel panel= new JPanel();panel.add(jbtSuspend);panel.add(jbtResume);ball.setBorder(new javax.swing.border.LineBorder(Color.red));jsbDelay.setOrientation(JScrollBar.HORIZONTAL);ball.setDelay(jsbDelay.getMaximum());setLayout(new BorderLayout());add(jsbDelay,BorderLayout.NORTH);add(ball,BorderLayout.CENTER);add(panel,BorderLayout.SOUTH);jbtSuspend.addActionListener(new ActionListener(){publicvoid actionPerformed(ActionEvent e){ball.suspend();}});jbtResume.addActionListener(new ActionListener(){publicvoid actionPerformed(ActionEvent e){ball.resume();}});jsbDelay.addAdjustmentListener(new AdjustmentListener(){ publicvoid adjustmentValueChanged(AdjustmentEvent e){ball.setDelay(jsbDelay.getMaximum()-e.getValue());}});}}import java.awt.*;importimport java.awt.event.*;import java.applet.*;publicclass BounceBallApp extends JApplet{public BounceBallApp(){add(new BallControl());}}。