自考Java语言程序设计(一)课后习题及答案(7)

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过文本显示转换后的摄氏温度。使用下面的公式进行温度转换：

摄氏温度=5/9Χ(华氏温度-32)

8．编写一个程序，使用户能够使用鼠标在applet中绘制一个矩形。按住鼠标左键，确定矩形的左上角，然后拖动鼠标，在需要的位置（即矩形右下角）释放鼠标。另外，在状态栏中显示矩形面积。

参考答案 1.false 2.true

3. CheckboxGroup 4.D 5． C

6. 参考程序如下：

import javawt.*;来源：考试大 import javawt.event.*;

public class Chp9_3_C extends Frame implements ActionListener{ TextField textField1,textField2,textField3; Button button1=new Button(\求和\ Panel panel1,panel2; public Chp9_3_C(){

textField1=new TextField(); textField2=new TextField(); textField3=new TextField(); panel1=new Panel(); panel2=new Panel();

panel1.setLayout(new GridLayout(3,2)); panel2.setLayout(new FlowLayout()); panel1.add(new Label(\数学: \ panel1.add(textField1);

panel1.add(new Label(\英语: \ panel1.add(textField2);

panel1.add(new Label(\总分: \ panel1.add(textField3); panel2.add(button1);

add(panel1,BorderLayout.CENTER); add(panel2,BorderLayout.SOUTH); button1.addActionListener(this); setSize(300,200); setVisible(true); }

public static void main(String[] args){ new Chp9_3_C(); }

public void actionPerformed(ActionEvent e){ int n1,n2,sum;

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n1=Integer.parseInt(textField1.getText()); n2=Integer.parseInt(textField2.getText()); sum=n1+n2;

textField3.setText(\} }

6．参考程序如下： import javawt.*;

import javawt.event.*;

public class Chp9_3_D extends Frame{ TextField textField1,textField2; Button button1; public Chp9_3_D(){

textField1=new TextField(30); textField2=new TextField(30); button1=new Button(\转换\setLayout(new FlowLayout()); add(new Label(\华氏温度：\add(textField1);

add(new Label(\摄氏温度：\add(textField2);

textField2.setEditable(false); add(button1); setSize(400,300); pack();

button1.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent e){ button1_actionPerformed(e); } });

addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ System.exit(0); } }); }

public static void main(String[] args){ new Chp9_3_D().setVisible(true); }

private void button1_actionPerformed(ActionEvent e){ double d=Double.parseDouble(textField1.getText()); double h=5.0/9.0*(d-32); textField2.setText(\}

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}

7．参考程序如下： import javapplet.Applet; import javawt.*;

import javawt.event.*; public class Chp9_3_E MouseListener,MouseMotionListener{

int x1,y1,x2,y2; public void init(){

addMouseListener(this);

addMouseMotionListener(this); }

public void paint(Graphics g){ g.drawRect(x1,y1,x2,y2);

int area=Math.abs(x2-x1)*Math.abs(y2-y1); showStatus(\矩形面积: \ }

//implementation of MouseListener

public void mousePressed(MouseEvent e){ x1=e.getX(); y1=e.getY(); }

public void mouseClicked(MouseEvent e){} public void mouseEntered(MouseEvent e){} public void mouseExited(MouseEvent e){} public void mouseReleased(MouseEvent e){} //implementation of MouseMotionEvent public void mouseDragged(MouseEvent e){ x2=e.getX(); y2=e.getY(); repaint(); }

public void mouseMoved(MouseEvent e){} }

extends Applet implements