Java面向对象程序设计课后答案(6)

习题11 1．A 2

． import java.awt.event.*; import java.awt.*; import javax.swing.*;

class Dwindow extends Frame implements ActionListener { TextField inputNumber; TextArea save; Dwindow(String s) { super(s);

inputNumber=new TextField(22); inputNumber.addActionListener(this); save=new TextArea(12,16); setLayout(new FlowLayout()); add(inputNumber); add(save);

setBounds(60,60,300,300); setVisible(true); validate();

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

public void actionPerformed(ActionEvent event) { String s=inputNumber.getText(); double n=0;

try{ n=Double.parseDouble(s); if(n>1000)

{ int select=JOptionPane.showConfirmDialog(this,"已经超过1000确认正确吗？","确认对话框", JOptionPane.YES_NO_OPTION ); if(select==JOptionPane.YES_OPTION) { save.append("\\n"+s); } else

{ inputNumber.setText(null);

} } else

{ save.append("\\n"+s); } }

catch(NumberFormatException e)

{ JOptionPane.showMessageDialog(this,"您输入了非法字符","警告对话框",

JOptionPane.WARNING_MESSAGE); inputNumber.setText(null); } } }

public class E

{ public static void main(String args[]) { new Dwindow("带对话框的窗口"); } }

3．参照以下例子完成 Xiti3.java public class Xiti3 {

public static void main(String args[]) { WindowColor win=new WindowColor();

win.setTitle("带颜色对话框的窗口"); } }

WindowColor.java import java.awt.event.*; import java.awt.*; import javax.swing.*;

public class WindowColor extends JFrame implements ActionListener { JButton button; WindowColor() {

button=new JButton("打开颜色对话框"); button.addActionListener(this); setLayout(new FlowLayout()); add(button);

setBounds(60,60,300,300); setVisible(true);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); }

public void actionPerformed(ActionEvent e) {

Color newColor=JColorChooser.showDialog(this,"调色板",button.getBackground());

if(newColor!=null) {

button.setBackground(newColor); } } }

习题12

1．使用FileInputStream流。

2．FileInputStream按字节读取文件，FileReader按字符读取文件。 3．不能。

4．使用对象流写入或读入对象时，要保证对象是序列化的。 5．使用对象流很容易得获取一个

序列化对象的克隆，只需将该对象写入到对象输出流，那么用对象输入流读回的对象一定是原对象的一个克隆。 6．

import java.io.*; public class Xiti6

{ public static void main(String args[]) { File f=new File("E.java");;

try{ RandomAccessFile random=new RandomAccessFile(f,"rw"); random.seek(0); long m=random.length(); while(m>=0) { m=m-1; random.seek(m); int c=random.readByte(); if(c<=255&&c>=0) { System.out.print((char)c); } else { m=m-1; random.seek(m); byte cc[]=new byte[2]; random.readFully(cc);

System.out.print(new String(cc)); } } }

catch(Exception exp){} } } 7．

import java.io.*; public class Xiti7

{ public static void main(String args[ ]) { File file=new File("E.java"); File tempFile=new File("temp.txt");

try{ FileReader inOne=new FileReader(file); BufferedReader inTwo= new BufferedReader(inOne); FileWriter tofile=new FileWriter(tempFile); BufferedWriter out= new BufferedWriter(tofile); String s=null; int i=0;

s=inTwo.readLine(); while(s!=null) { i++;

out.write(i+" "+s); out.newLine(); s=inTwo.readLine(); }

inOne.close(); inTwo.close(); out.flush(); out.close(); tofile.close(); }

catch(IOException e) { System.out.println(e); } } }

8．属于操作题目，解答略。 9．

import java.util.*; import java.io.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class Xiti9

{ public static void main(String args[]) { EWindow w=new EWindow(); w.validate(); } }

class EWindow extends Frame implements ActionListener,ItemListener { String str[]=new String[7],s; FileReader file; BufferedReader in; Button start,next; Checkbox checkbox[]; TextField 题目,分数;