Java面向对象程序设计复习题附答案解析

}

四、程序填空题

1.以下程序是一个算术测试小软件，用来训练小学生的算术能力。程序有3个类组成，其中Teacher对象充当监视器，负责给出算术题目，并判断回答者的答案是否正确。ComputerFrame对象负责为算术题目提供视图，比如用户可以通过ComputerFrame对象提供的GUI界面看到题目，并通过该GUI界面给出题目的答案；MailClass是软件的主类。

程序运行效果如下图所示。

仔细阅读程序代码，请按模板要求，在【代码】处填写合适的Java程序代码。

MainClass.java

public class MainClass {

public static void main(String args[]) { ComputerFrame frame;

frame=new ComputerFrame(); frame.setTitle(\算术测试\

frame.setBounds(100,100,650,180); } }

ComputerFrame.java

import java.awt.*;

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

public class ComputerFrame extends JFrame { JMenuBar menubar;

JMenu choiceGrade; //选择级别的菜单 JMenuItem grade1,grade2;

JTextField textOne,textTwo,textResult; JButton getProblem,giveAnwser; JLabel operatorLabel,message; Teacher teacherZhang; ComputerFrame() {

teacherZhang=new Teacher(); teacherZhang.setMaxInteger(20);

setLayout(【代码1】_new FlowLayout()________________________________); //设置ComputerFrame的布局为FlowLayout布局

menubar = new JMenuBar();

choiceGrade = new JMenu(\选择级别\ grade1 = new JMenuItem(\幼儿级别\ grade2 = new JMenuItem(\儿童级别\

grade1.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) { teacherZhang.setMaxInteger(10); } });

grade2.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) { teacherZhang.setMaxInteger(50); } }); choiceGrade.add(grade1); choiceGrade.add(grade2); menubar.add(choiceGrade); setJMenuBar(menubar);

【代码1】__ textOne=new JTextField(5);_________________________________ //创建textOne,其可见字符长是5 textTwo=new JTextField(5); textResult=new JTextField(5); operatorLabel=new JLabel(\

operatorLabel.setFont(new Font(\ message=new JLabel(\你还没有回答呢\ getProblem=new JButton(\获取题目\ giveAnwser=new JButton(\确认答案\ add(getProblem); add(textOne);

add(operatorLabel); add(textTwo);

add(new JLabel(\ add(textResult); add(giveAnwser); add(message);

textResult.requestFocus(); textOne.setEditable(false); textTwo.setEditable(false);

getProblem.setActionCommand(\ textResult.setActionCommand(\ giveAnwser.setActionCommand(\

teacherZhang.setJTextField(textOne,textTwo,textResult); teacherZhang.setJLabel(operatorLabel,message);

【代码2】_______ getProblem.addActionListener(teacherZhang); ____________ //将teacherZhang注册为getProblem的ActionEvent事件监视器

【代码3】_____giveAnwser.addActionListener(teacherZhang); ___//将teacherZhang注册为giveAnwser的ActionEvent事件监视器

【代码4】__________textResult.addActionListener(teacherZhang); __//将teacherZhang注册为textResult的ActionEvent事件监视器 setVisible(true); validate();

setDefaultCloseOperation(DISPOSE_ON_CLOSE); } }

Teacher.java

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

public class Teacher implements ActionListener { int numberOne,numberTwo; String operator=\ boolean isRight;

Random random; //用于给出随机数 int maxInteger; //题目中最大的整数 JTextField textOne,textTwo,textResult; JLabel operatorLabel,message; Teacher() {

random = new Random(); }

public void setMaxInteger(int n) { maxInteger=n; }

public void actionPerformed(ActionEvent e) { String str = e.getActionCommand(); if(str.equals(\

numberOne = random.nextInt(maxInteger)+1;//1至maxInteger之间的随机数; numberTwo=random.nextInt(maxInteger)+1;

double d=Math.random(); // 获取(0,1)之间的随机数 if(d>=0.5)

operator=\ else

operator=\

textOne.setText(\ textTwo.setText(\ operatorLabel.setText(operator); message.setText(\请回答\ textResult.setText(null); }

else if(str.equals(\

String answer=textResult.getText();

try{ int result=Integer.parseInt(answer); if(operator.equals(\

if(result= =numberOne+numberTwo) message.setText(\你回答正确\ else

message.setText(\你回答错误\ }

else if(operator.equals(\

if(result= =numberOne-numberTwo) message.setText(\你回答正确\ else

message.setText(\你回答错误\ } }

catch(NumberFormatException ex) {

message.setText(\请输入数字字符\ } } }

public void setJTextField(JTextField ... t) { textOne=t[0]; textTwo=t[1]; textResult=t[2]; }

public void setJLabel(JLabel ...label) { operatorLabel=label[0]; message=label[1]; } }

2. 有如下 java源程序，程序的功能是在数组中查找键盘键入的整数。如果找到则输出该整数在数组中的序号，否则输出“not found”。例如，运行程序，输入99，程序输出：99在数组中的序号是5；输入 59，程序输出：not found。

仔细阅读程序代码，请按模板要求，在【代码】处填写合适的Java程序代码。（注意： 不改动程序的结构，不得增行或删行）。 import java.io.*;

import java.util.Scanner; public class J_Test {

public static void main(String[] args) throws IOException {

int 【代码1】________a[]_____________ = {83,75,92,67,55,99,78,61}; Scanner in = new Scanner(【代码2】___System.in_________________); int x = Integer.parseInt(【代码3】__________in.readLine()_________); int index = -1;

for(int i = 0; 【代码4】___i<=a..Length_____________________; ++i) {

if(a[i] == x) { index = i; break; } }

if(【代码5】_____index==-1____________________________) System.out.println(\ else

System.out.println(x + \在数组中的序号是\ } }

3. 下面程序的运行结果如下图。单击“Close”按钮关闭窗口。

请阅读程序，在（1）和（2）处补充相应的内容，使整个程序能够正常运行。 import java.awt.*;

import java.awt.event.*; import javax.swing.*; public class J_Test { private JFrame f;

private JButton button1, button2, button3; public void go() {

f = new JFrame(\

f.setLayout(new FlowLayout()); button1 = new JButton(\ button2 = new JButton(\ button3 = new JButton(\ f.add(button1); f.add(button2); f.add(button3);

____ button3.addActionListener(new Monitor()); ________ f.setSize(160, 106); f.setVisible(true); }

public static void main(String[] args) { J_Test t = new J_Test(); t.go(); } }

class Monitor implements ActionListener {