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Java2實用教程（第4版）

耿祥義、張躍平 / 清華大學出版社

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習題九（第9章）

一、問答題

1．Frame容器的默認布局是BorderLayout布局。

2．不可以。

3．ActionEvent。

4．DocumentEvent。

5．5個。

6．MouseMotionListener。

二、選擇題

1．C。2．A。3．A。4．D。5．C。

三、編程題

1． import java.awt.*;

import javax.swing.event.*;

import javax.swing.*;

import java.awt.event.*;

public class E {

???public static void main(String args[]) {

??????Computer fr=new Computer();

???}

}

class Computer extends JFrame implements DocumentListener {

???JTextArea text1,text2;

???int count=1;

???double sum=0,aver=0;

???Computer() {

??????setLayout(new FlowLayout());

??????text1=new JTextArea(6,20);

??????text2=new JTextArea(6,20);

??????add(new JScrollPane(text1));

??????add(new JScrollPane(text2));

??????text2.setEditable(false);

??????(text1.getDocument()).addDocumentListener(this);

??????setSize(300,320);

??????setVisible(true);

??????validate();

??????setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

???}

???public void changedUpdate(DocumentEvent e) {

??????String s=text1.getText();

??????String []a =s.split("[^0123456789.]+");

??????sum=0;

??????aver=0; ?

??????for(int i=0;i<a.length;i++) {

????????try { sum=sum+Double.parseDouble(a[i]);

????????}

????????catch(Exception ee) {}

?????}

?????aver=sum/count;

?????text2.setText(null);

?????text2.append("\n和:"+sum);

?????text2.append("\n平均值:"+aver);

???}

???public void removeUpdate(DocumentEvent e){

??????changedUpdate(e); ?

???}

???public void insertUpdate(DocumentEvent e){

??????changedUpdate(e);

???}

}

2. ??import java.awt.*;

import javax.swing.event.*;

import javax.swing.*;

import java.awt.event.*;

public class E {

???public static void main(String args[]) {

??????ComputerFrame fr=new ComputerFrame();

???}

}

class ComputerFrame extends JFrame implements ActionListener {

??JTextField text1,text2,text3;

??JButton buttonAdd,buttonSub,buttonMul,buttonDiv;

??JLabel label;

??public ComputerFrame() {

???setLayout(new FlowLayout());

???text1=new JTextField(10);

???text2=new JTextField(10);

???text3=new JTextField(10);

???label=new JLabel(" ",JLabel.CENTER);

???label.setBackground(Color.green);

???add(text1);

???add(label);

???add(text2);

???add(text3);

???buttonAdd=new JButton("加"); ???

???buttonSub=new JButton("減");

???buttonMul=new JButton("乘");

???buttonDiv=new JButton("除");

???add(buttonAdd);

???add(buttonSub);

???add(buttonMul);

???add(buttonDiv);

???buttonAdd.addActionListener(this);

???buttonSub.addActionListener(this);

???buttonMul.addActionListener(this); ?

???buttonDiv.addActionListener(this);

???setSize(300,320);

???setVisible(true);

???validate();

???setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

??} ??

??public void actionPerformed(ActionEvent e) {

????double n;

????if(e.getSource()==buttonAdd) {

???????double n1,n2; ?

???????try{ n1=Double.parseDouble(text1.getText());

????????????n2=Double.parseDouble(text2.getText());

????????????n=n1+n2;

????????????text3.setText(String.valueOf(n));

????????????label.setText("+");

??????????}

???????catch(NumberFormatException ee)

??????????{ text3.setText("請輸入數(shù)字字符");

??????????}

?????}

????else if(e.getSource()==buttonSub) {

???????double n1,n2; ?

???????try{ ?n1=Double.parseDouble(text1.getText());

????????????n2=Double.parseDouble(text2.getText());

????????????n=n1-n2;

????????????text3.setText(String.valueOf(n));

????????????label.setText("-");

??????????}

???????catch(NumberFormatException ee)

??????????{ text3.setText("請輸入數(shù)字字符");

??????????}

?????}

?????else if(e.getSource()==buttonMul)

??????{double n1,n2; ?

???????try{ n1=Double.parseDouble(text1.getText());

????????????n2=Double.parseDouble(text2.getText());

????????????n=n1*n2;

????????????text3.setText(String.valueOf(n));

????????????label.setText("*");

??????????}

???????catch(NumberFormatException ee)

??????????{ text3.setText("請輸入數(shù)字字符");

??????????}

??????}

??????else if(e.getSource()==buttonDiv)

??????{double n1,n2; ?

???????try{ n1=Double.parseDouble(text1.getText());

????????????n2=Double.parseDouble(text2.getText());

????????????n=n1/n2;

????????????text3.setText(String.valueOf(n));

????????????label.setText("/");

??????????}

???????catch(NumberFormatException ee)

??????????{ text3.setText("請輸入數(shù)字字符");

??????????}

??????}

?????validate();

??}

}

3.???import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class E {

???public static void main(String args[]){

??????Window win = new Window();

??????win.setTitle("使用MVC結構");

??????win.setBounds(100,100,420,260);

???}

}

class Window extends JFrame implements ActionListener {

???Lader lader; ????????????//模型

???JTextField textAbove,textBottom,textHeight; ??//視圖

???JTextArea showArea; ????????//視圖

???JButton controlButton; ???????//控制器

???Window() {

??????init();

??????setVisible(true);

??????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

???}

???void init() {

?????lader = new Lader();

?????textAbove = new JTextField(5); ??

?????textBottom = new JTextField(5);

?????textHeight = new JTextField(5);

?????showArea = new JTextArea(); ???

?????controlButton=new JButton("計算面積");

?????JPanel pNorth=new JPanel();

?????pNorth.add(new JLabel("上底:"));

?????pNorth.add(textAbove);

?????pNorth.add(new JLabel("下底:"));

?????pNorth.add(textBottom);

?????pNorth.add(new JLabel("高:"));

?????pNorth.add(textHeight);

?????pNorth.add(controlButton);

?????controlButton.addActionListener(this);

?????add(pNorth,BorderLayout.NORTH);

?????add(new JScrollPane(showArea),BorderLayout.CENTER);

???}

???public void actionPerformed(ActionEvent e) {

?????try{ ?

????????double above = Double.parseDouble(textAbove.getText().trim());

????????double bottom = Double.parseDouble(textBottom.getText().trim());

????????double height = Double.parseDouble(textHeight.getText().trim());

????????lader.setAbove(above) ; ?????????

????????lader.setBottom(bottom);

????????lader.setHeight(height);

????????double area = lader.getArea(); ????

????????showArea.append("面積:"+area+"\n");

?????}

?????catch(Exception ex) {

????????showArea.append("\n"+ex+"\n");

?????}

???}

}

class Lader {

????double above,bottom,height;

????public double getArea() {

???????double area = (above+bottom)*height/2.0;

???????return area;

????}

????public void setAbove(double a) {

??????above = a;

????}

???public void setBottom(double b) {

??????bottom = b;

???}

???public void setHeight(double c) {

?????height = c;

???}

}

習題十（第10章）

一、問答題

1．使用FileInputStream。

2．FileInputStream按字節(jié)讀取文件，FileReader按字符讀取文件。

3．不可以。

4．使用對象流寫入或讀入對象時，要保證對象是序列化的。

5．使用對象流很容易得獲取一個序列化對象的克隆，只需將該對象寫入到對象輸出流，那么用對象輸入流讀回的對象一定是原對象的一個克隆。

二、選擇題

1．C。2．B。

三、閱讀程序

1．【代碼1】：51?！敬a2】：0。

2．【代碼1】：3?！敬a2】：abc。【代碼3】：1。【代碼4】：dbc。

3．上機實習題，解答略。

四、編程題

1． import java.io.*;

public class E {

???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){}

????}

}

2. ??import java.io.*;

public class E {

???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){}

???}

}

3.???import java.io.*;

import java.util.*;

public class E {

???public static void main(String args[]) {

??????File file = new File("a.txt");

??????Scanner sc = null;

??????double sum=0;

??????int count = 0;

??????try { sc = new Scanner(file);

????????????sc.useDelimiter("[^0123456789.]+");

????????????while(sc.hasNext()){

???????????????try{ ?double price = sc.nextDouble();

????????????????????count++;

????????????????????sum = sum+price;

????????????????????System.out.println(price);

???????????????}

???????????????catch(InputMismatchException exp){

????????????????????String t = sc.next();

???????????????} ??

????????????}

????????????System.out.println("平均價格:"+sum/count);

??????}

??????catch(Exception exp){

?????????System.out.println(exp);

??????}

???}

}


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