java 期末复习题目练习

xiaoxiao2021-02-28  17

1 打印出所有的"水仙花数",所谓"水仙花数"是指一个三位数,其各位数字立方和等于该数本身。例如:153 是一个"水仙花数",因为153=1的三次方+5的三次方+3的三次方。

package one; public class Shuixianhua { public static void main(String[] args) { System.out.println("所有的水仙花数:"); for (int i = 100; i < 1000; i++) { int ge,shi,bai; bai=i/100; shi=(i-100*bai)/10; ge=i-bai*100-shi*10; if(i==bai*bai*bai+shi*shi*shi+ge*ge*ge){ System.out.println(i+""); } } } }

2 建立一个长度为9的数组,随机为该数组分配九个0~100间的随机数作为数组元素,并顺序打印数组元素;然后实现数组反转,并打印反转后的数组元素。

package two; import java.util.Random; public class RandomNum { public static void main(String[] args) { int[] a=new int[9]; for (int i = 0; i < a.length; i++) { a[i]=(int)(Math.random()*100)+1; } System.out.println("顺序输出随机数:"); for (int i = 0; i < a.length; i++) { System.out.println("a["+i+"]="+a[i]); } for (int i = 0; i < a.length/2; i++) { int temp=a[i]; a[i]=a[a.length-i-1]; a[a.length-i-1]=temp; } System.out.println("数组反转后:"); for (int i = 0; i < a.length; i++) { System.out.println("a["+i+"]="+a[i]); } } }

3 编写程序模拟体操比赛选手成绩的计算方法。首先输入五位评委各自的打分(满分100分),去掉一个最高分、去掉一个最低分后求平均分(保留小数点后两位)作为选手的最终成绩并输出。

package three; import java.util.Scanner; public class Score { public static void main(String[] args) { System.out.println("请各评委输入8号选手的成绩:"); Scanner in = new Scanner(System.in); double a[] = new double[5]; for(int i=0; i<5; i++){ a[i]=in.nextDouble(); } System.out.println("五位评委分别打分为:"); for(int i=0; i<5; i++) System.out.print(" "+a[i]); System.out.println(); double avg=0; //对数组的值进行冒泡排序 for (int i = 1; i < a.length; i++) { for (int j = 0; j < a.length-i; j++) { if (a[j]>a[j+1]) { double temp=a[j]; a[j]=a[j+1]; a[j+1]=temp; } } } for(int i=0; i<5; i++) avg+=a[i]; System.out.println("8号选手的最终得分是:"+((avg-a[a.length-1]-a[0])/5)); } }

4 编写一个应用程序,用户分别从两个文本框输入学生的姓名和分数,程序按成绩排序将这些学生的姓名和分数显示在一个文本区中。 程序以及运行效果如图:

package four; import java.awt.*; import javax.swing.*; import java.awt.event.*; import java.util.*; public class StudentFrame extends JFrame{ JPanel pl; JLabel name, score; JTextField inputName, inputScore; JButton button; JScrollPane sp; JTextArea showArea; TreeSet<Student> treeSet; StudentFrame(String title){ super(title); treeSet = new TreeSet<Student>(); pl = new JPanel(); name = new JLabel("姓名"); score = new JLabel("成绩"); inputName = new JTextField(5); inputScore = new JTextField(5); button = new JButton("确定"); button.addActionListener(new MyListener()); pl.add(name); pl.add(inputName); pl.add(score); pl.add(inputScore); pl.add(button); showArea = new JTextArea(); sp = new JScrollPane(showArea); add(pl, BorderLayout.NORTH); add(sp, BorderLayout.CENTER); setSize(400,300); setVisible(true); validate(); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } class MyListener implements ActionListener{ public void actionPerformed(ActionEvent e){ String name = inputName.getText(); int score = 0; try{ score = Integer.parseInt(inputScore.getText().trim()); if(name.length()>0){ Student stu = new Student(name, score); treeSet.add(stu); show(treeSet); } }catch(NumberFormatException nfe){ inputScore.setText("请输入数字字符"); } } public void show(TreeSet tree){ showArea.setText(null); Iterator<Student> it = treeSet.iterator(); while(it.hasNext()){ Student stu = it.next(); showArea.append("姓名:"+stu.getName()+" 成绩:"+stu.getScore()+"\n"); } } } public static void main(String[] args) { new StudentFrame("学生成绩排序"); } } class Student implements Comparable{ String name; int score; Student(String name, int score){ this.name = name; this.score = score; } public int getScore(){ return score; } public String getName(){ return name; } public int compareTo(Object b){ Student st = (Student)b; int m = this.score - st.getScore(); if (m!=0) return m; else return 1; } }

5 有10个U盘,有两个重要的属性:价格和容量。编写一个应用程序,使用TreeMap<>类,分别按照价格和容量排序输出10个U盘的详细信息。

package five; import java.util.Collection; import java.util.Iterator; import java.util.TreeMap; public class UDisk { int amount; double price; UDisk(int amount, double price){ this.amount = amount; this.price = price; } } class UKey implements Comparable{ double key = 0; UKey(double key){ this.key = key; } public int compareTo(Object b){ UKey bb = (UKey)b; if(this.key == bb.key) return -1; else return (int)((this.key-bb.key)*1000); } } class E{ public static void main(String[] args) { TreeMap<UKey, UDisk> treemap = new TreeMap<UKey, UDisk>(); int amount[] = {1, 2, 4, 8, 16, 32}; double price[] = {25, 18, 32, 80, 64, 120}; UDisk ud[] = new UDisk[6]; for(int i=0; i<ud.length; i++) ud[i] = new UDisk(amount[i], price[i]); UKey ukey[] = new UKey[6]; for(int i=0; i<ud.length; i++) ukey[i] = new UKey(ud[i].amount); for(int i=0; i<ud.length; i++) treemap.put(ukey[i], ud[i]); Collection<UDisk> c = treemap.values(); Iterator<UDisk> it = c.iterator(); while(it.hasNext()){ UDisk d = it.next(); System.out.println("容量"+d.amount+"GB,"+d.price+"元"); } treemap.clear(); System.out.println("--------------------------------------"); for(int i=0; i<ud.length; i++) ukey[i] = new UKey(ud[i].price); for(int i=0; i<ud.length; i++) treemap.put(ukey[i], ud[i]); c = treemap.values(); it = c.iterator(); while(it.hasNext()){ UDisk d = it.next(); System.out.println("容量"+d.amount+"GB,"+d.price+"元"); } } }

6 编写一个简易计算器,有一个标题为“简易计算器”的窗口。设计 “+”、“-”、“*”、“/”四种运算,另外,窗口中还有三个文本框。单击相应的按钮,将两个文本框的数字做运算,在第三个文本框中显示结果。要求处理NumberFormatException异常。程序运行效果如下图:

package six; import java.awt.*; import javax.swing.*; import java.awt.event.*; public class Calculator extends JFrame implements ActionListener{ JTextField text1, text2, text3; JRadioButton btnAdd, btnSub, btnMul, btnDiv; ButtonGroup bg; JLabel num1, num2, result; JButton solve; Box base, boxH1, boxH2, boxH3, boxH4; public Calculator(String name){ super(name); setLayout(new FlowLayout()); text1 = new JTextField(10); text2 = new JTextField(10); text3 = new JTextField(10); btnAdd = new JRadioButton("+"); btnSub = new JRadioButton("-"); btnMul = new JRadioButton("*"); btnDiv = new JRadioButton("/"); num1 = new JLabel("数一"); num2 = new JLabel("数二"); result = new JLabel("结果"); solve = new JButton("="); solve.addActionListener(this); bg = new ButtonGroup(); bg.add(btnAdd); bg.add(btnSub); bg.add(btnMul); bg.add(btnDiv); boxH1 = Box.createHorizontalBox(); boxH1.add(num1); boxH1.add(Box.createHorizontalStrut(30)); boxH1.add(text1); boxH2 = Box.createHorizontalBox(); boxH2.add(btnAdd); boxH2.add(btnSub); boxH2.add(btnMul); boxH2.add(btnDiv); boxH3 = Box.createHorizontalBox(); boxH3.add(num2); boxH3.add(Box.createHorizontalStrut(30)); boxH3.add(text2); boxH4 = Box.createHorizontalBox(); boxH4.add(result); boxH4.add(Box.createHorizontalStrut(30)); boxH4.add(text3); base = Box.createVerticalBox(); base.add(boxH1); base.add(Box.createVerticalStrut(25)); base.add(boxH2); base.add(Box.createVerticalStrut(25)); base.add(boxH3); base.add(Box.createVerticalStrut(25)); base.add(solve); base.add(Box.createVerticalStrut(25)); base.add(boxH4); add(base); setSize(300, 320); setVisible(true); validate(); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); } public void actionPerformed(ActionEvent e){ double n = 0; double n1,n2; try{ n1=Double.parseDouble(text1.getText()); n2=Double.parseDouble(text2.getText()); if(btnAdd.isSelected()) n = n1+n2; else if(btnSub.isSelected()) n = n1-n2; else if(btnMul.isSelected()) n = n1*n2; else if(btnDiv.isSelected()) n = n1/n2; text3.setText(String.valueOf(n)); }catch(NumberFormatException nfe){ text3.setText("请输入数字字符"); } } public static void main(String args[]){ new Calculator("简易计算器"); } }

7 请写一个简易计时器。单击“开始”按钮启动计时器,并将计时时间显示在文本框中;单击“暂停”按钮暂停计时器;单击“继续”按钮重新启动计时器。程序运行效果如下图:

package seven; import java.awt.*; import javax.swing.*; import java.awt.event.*; public class MyTimer extends JFrame implements ActionListener { JTextField text; JButton bStart, bStop, bContinue; Timer time; int n = 0; MyTimer(String name){ super(name); time = new Timer(1000, this); text = new JTextField(15); bStart = new JButton("开始"); bStop = new JButton("暂停"); bContinue = new JButton("继续"); bStart.addActionListener(this); bStop.addActionListener(this); bContinue.addActionListener(this); setLayout(new FlowLayout()); add(bStart); add(bStop); add(bContinue); add(text); setSize(300, 120); setVisible(true); validate(); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); } public void actionPerformed(ActionEvent e){ if(e.getSource()==time){ n = n + 1; text.setText("计时:"+ n +"秒"); } else if(e.getSource()==bStart){ n = 0; time.start(); } else if(e.getSource()==bStop) time.stop(); else if(e.getSource()==bContinue) time.restart(); } public static void main(String[] args) { new MyTimer("简易计时器"); } }

8 编写多线程程序,模拟多个人通过一个山洞。这个山洞每次只能通过一个人,每个人通过山洞的时间为2秒(sleep)。随机生成10个人,都要通过此山洞,用随机值对应的字符串表示人名,打印输出每次通过山洞的人名。提示:利用线程同步机制,过山洞用一条输出语句表示,该输出语句打印输出当前过山洞的人名,每个人过山洞对应一个线程,哪个线程执行这条输出语句,就表示哪个人过山洞。

package eight; import java.util.Random; public class PassCave implements Runnable{ public void run() { synchronized (this) { System.out.println(Thread.currentThread().getName()+"正在通过山洞"); try{ Thread.sleep(2000); }catch(InterruptedException ie){ ie.printStackTrace(); } } } public static String getRandomString(int length) { //length表示生成字符串的长度 String base = "abcdefghijklmnopqrstuvwxyz0123456789"; Random random = new Random(); StringBuffer sb = new StringBuffer(); for (int i = 0; i < length; i++) { int number = random.nextInt(base.length()); sb.append(base.charAt(number)); } return sb.toString(); } public static void main(String[] args) { PassCave pc = new PassCave(); Thread th[] = new Thread[10]; for(int i=0; i<10; i++){ th[i] = new Thread(pc); th[i].setName(getRandomString(5)); th[i].start(); } } }

9 用两个线程玩猜数字游戏,第一个线程负责随机给出1~100之间的一个整数,第二个线程负责猜出这个数。要求每当第二个线程给出自己的猜测后,第一个线程都会提示“猜小了”、“猜大了”或“猜对了”。猜数之前,要求第二个线程要等待第一个线程设置好要猜测的数。第一个线程设置好猜测数之后,两个线程还要相互等待,其原则是:第二个线程给出自己的猜测后,等待第一个线程给出的提示;第一个线程给出提示后,等待给第二个线程给出猜测,如此进行,直到第二个线程给出正确的猜测后,两个线程进入死亡状态。

package nine; public class GuessNumber { public static void main(String args[]){ Number number = new Number(); number.giveNumberThread.start(); number.guessNumberThread.start(); } } class Number implements Runnable{ final int SMALLER = -1, LARGER = 1, SUCCESS = 8; int realNumber, guessNumber, min = 0, max = 100, message = SMALLER; boolean pleaseGuess = false, isGiveNumber = false; Thread giveNumberThread, guessNumberThread; Number(){ giveNumberThread = new Thread(this); guessNumberThread = new Thread(this); } public void run(){ for(int count =1; true; count++){ setMessage(count); if(message == SUCCESS) return; } } public synchronized void setMessage(int count){ if(Thread.currentThread() == giveNumberThread && isGiveNumber == false){ realNumber = (int)(Math.random()*100)+1; System.out.println("随机给你一个1至100之间的数,猜猜是多少?"); isGiveNumber = true; pleaseGuess = true; } if(Thread.currentThread() == giveNumberThread){ while(pleaseGuess == true) try{ wait(); //让出CPU使用权,让另一个线程开始猜数 }catch(InterruptedException e){ } if(realNumber > guessNumber){ message = SMALLER; System.out.println("你猜小了!"); } else if(realNumber < guessNumber){ message = LARGER; System.out.println("你猜大了!"); } else { message = SUCCESS; System.out.println("恭喜,你猜对了!"); } pleaseGuess = true; } if(Thread.currentThread() == guessNumberThread && isGiveNumber == true){ while(pleaseGuess == false) try{ wait(); //让出CPU使用权,让另一个线程开始猜数 }catch(InterruptedException e){ } if(message == SMALLER){ min = guessNumber; guessNumber = (min + max)/2; System.out.println("我第"+count+"次猜这个数是"+guessNumber); } else if(message == LARGER){ max = guessNumber; guessNumber = (min + max)/2; System.out.println("我第"+count+"次猜这个数是"+guessNumber); } pleaseGuess = false; } notifyAll(); } }

10 在电视节目中经常看见主持人提出的问题,并要求考试者在限定时间内回答问题。这里由程序提出问题,用户回答问题。问题保存在test.txt中,test.txt的格式如下。 每个问题提供A、B、C、D四个选择(单项选择)。 两个问题之间是用减号(-)尾加前一问题的答案分隔(例如:----D----)。 使用GUI界面,增加一个辅助限制答题时间的计时器线程,该线程限制用户必须在10秒内回答问题,一旦超过10秒,将进入下一题。程序运行效果如下图:

package ten; import java.awt.*; import javax.swing.*; import java.awt.event.*; import java.io.*; public class Exam extends JFrame implements ActionListener, ItemListener{ File test; int MAX = 10; int maxTime = MAX, score = 0; javax.swing.Timer time; JTextArea showQuestion; JCheckBox choiceA, choiceB, choiceC, choiceD; JLabel showScore, showTime; String correctAnswer; JButton reStart; FileReader inOne; BufferedReader inTwo; Box base, boxH1, boxH2; Exam(String title){ super(title); time = new javax.swing.Timer(1000, this); showQuestion = new JTextArea(2, 16); setLayout(new FlowLayout()); showScore = new JLabel("分数"+score); showTime = new JLabel(" "); boxH1 = Box.createHorizontalBox(); boxH1.add(showTime); boxH1.add(new JLabel("问题")); boxH1.add(showQuestion); choiceA = new JCheckBox("A"); choiceB = new JCheckBox("B"); choiceC = new JCheckBox("C"); choiceD = new JCheckBox("D"); choiceA.addItemListener(this); choiceB.addItemListener(this); choiceC.addItemListener(this); choiceD.addItemListener(this); boxH2 = Box.createHorizontalBox(); boxH2.add(choiceA); boxH2.add(choiceB); boxH2.add(choiceC); boxH2.add(choiceD); boxH2.add(showScore); reStart = new JButton("再做一遍"); reStart.setEnabled(false); reStart.addActionListener(this); boxH2.add(reStart); base = Box.createVerticalBox(); base.add(boxH1); base.add(boxH2); add(base); setSize(400,200); setVisible(true); validate(); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); } public void setMAX(int n){ MAX = n; } public void setTestFile(File f){ test = f; score = 0; try{ inOne = new FileReader(test); inTwo = new BufferedReader(inOne); readOneQuestion(); reStart.setEnabled(false); }catch(IOException e){ showQuestion.setText("没有选题"); } } public void readOneQuestion(){ showQuestion.setText(null); try{ String s = null; while((s=inTwo.readLine())!=null){ if(!s.startsWith("-")) showQuestion.append("\n"+s); else{ s = s.replaceAll("-", ""); correctAnswer = s; break; } } time.start(); if(s==null){ inTwo.close(); reStart.setEnabled(true); showQuestion.setText("题目完毕"); time.stop(); } }catch(IOException e){ } } public void itemStateChanged(ItemEvent e){ JCheckBox box = (JCheckBox)e.getSource(); String str = box.getText(); boolean bOne = box.isSelected(); boolean bTwo = str.compareToIgnoreCase(correctAnswer)==0; if(bOne && bTwo){ score++; showScore.setText("分数"+score); time.stop(); maxTime = MAX; readOneQuestion(); } box.setSelected(false); } public void actionPerformed(ActionEvent e){ if(e.getSource()==time){ showTime.setText("剩:"+maxTime+"秒"); maxTime--; if(maxTime<=0){ maxTime = MAX; readOneQuestion(); } } else if(e.getSource()==reStart) setTestFile(test); } } class Answer{ public static void main(String[] args) { Exam win = new Exam("限时回答问题"); win.setTestFile(new File("D:\\","test.txt")); win.setMAX(10); } }

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