Java语言程序设计(基础篇)(第10版 梁勇著)第二章练习题答案

第一章1.1public class Test{public static void main(String[]args){System.out.println("Welcome to Java!"); System.out.println("Welcome to Computer Science!");System.out.println("Progr amming is fun.");}}1.2public class Test{public static void main(String[]args){for(int i=0;i<=4;i++){System.out.println("Welcome to Java!");}}}1.3public class Test{public static void main(String[]args){System.out.println("]");System.out.printl n("]");System.out.println("]]");System.out.println("]]");}}public class Test{public static void main(String[]args){System.out.println("A"); System.out.println("A A");System.out.println("AAAAA");System.out.println("A A");}}public class Test{public static void main(String[]args){System.out.println("V V");System.out.println("V V");System.out.println("V V");System.out.println(" V");}}1.4public class Test{public static void main(String[]args){System.out.println("a a^2a^3");System.out.println("111");System.out.println("248");System.out.println("3 927");System.out.println("41664");}}1.5public class Test{public static void main(String[]args){System.out.println((9.5*4.5-2.5*3)/(45.5-3.5) );}}1.6public class Test{public static void main(String[]args){int i=1,sum=0;for(;i<=9;i++)sum+ =i;System.out.println(sum);}1.7public class Test{public static void main(String[]args){System.out.println(4*(1.0-1.0/3+1.0/5-1.0/7+1.0/9-1.0/11));System.out.println(4*(1.0-1.0/3+1.0/5-1.0/7+1.0/9-1.0/11+1.0/13));}}1.8public class Test{public static void main(String[]args){final double PI=3.14; double radius=5.5;System.out.println(2*radius*PI);System.out.println(PI*radius*radius);}}1.9public class Test{public static void main(String[]args){System.out.println(7.9*4.5);System.out.p rintln(2*(7.9+4.5));}}1.10public class Test{public static void main(String[]args){double S=14/1.6;double T=45*60+30;double speed=S/T;System.out.println(speed);}1.11public class Test{public static void main(String[]args){int BN=312032486; //original person numbers double EveryYS,EveryYBP,EveryYDP,EveryYMP;EveryY S=365*24*60*60;EveryYBP=EveryYS/7;EveryYDP=EveryYS/13;Every YMP=EveryYS/45;int FirstYP,SecondYP,ThirdYP,FourthYP,FivthYP;FirstYP=(int)(BN+EveryYBP+EveryYMP-EveryYDP);SecondYP=(int)(FirstYP +EveryYBP+EveryYMP-EveryYDP);ThirdYP=(int)(SecondYP+EveryYBP+Ev eryYMP-EveryYDP);FourthYP=(int)(ThirdYP+EveryYBP+EveryYMP-EveryYD P);FivthYP=(int)(FourthYP+EveryYBP+EveryYMP-EveryYDP);System.out.pri ntln(FirstYP);System.out.println(SecondYP);System.out.println(ThirdYP);Syste m.out.println(FourthYP);System.out.println(FivthYP);}}1.12public class Test{public static void main(String[]args){double S=24*1.6; double T=(1*60+40)*60+35;double speed=S/T;System.out.println(sp eed);}}1.13import java.util.Scanner;public class Test{public static void main(String[]args){Scanner input=new Scan ner(System.in);System.out.println("input a,b,c,d,e,f value please:");double a=input.nextDouble();double b=input.nextDouble();double c=input.nextDouble();double d=input. nextDouble();double e=input.nextDouble();第二章package cn.Testcx;import java.util.Scanner;public class lesson2{public static void main(String[]args){@SuppressWarnings("resource")Scanner in put=new Scanner(System.in);System.out.print("请输入一个摄氏温度：");double Celsius=input.nextDouble();double Fahrenheit=(9.0/5)*Celsius+3 2;System.out.println("摄氏温度："+Celsius+"度"+"转换成华氏温度为："+Fahrenheit+"度");System.out.print("请输入圆柱的半径和高：");double radius=input.nextDouble();int higth=input.nextInt();double are as=radius*radius*Math.PI;double volume=areas*higth;System.out.println("圆柱体的面积为："+areas);System.out.println("圆柱体的体积为："+volume);System.out.print("输入英尺数：");double feet=input.nextDouble();double meters=feet*0.305;System.out.print ln(feet+"英尺转换成米："+meters);System.out.print("输入一个磅数：");double pounds=input.nextDouble();double kilograms=pounds*0.454;Syste m.out.println(pounds+"磅转换成千克为："+kilograms);System.out.println("输入分钟数：");long minutes=input.nextInt();long years=minutes/(24*60*365);long days=(minutes%(24*60*365))/(24*60);System.out.println(minutes+"分钟"+"有"+years+"年和"+days+"天");long totalCurrentTimeMillis=System.currentTimeMillis();long totalSeconds=t otalCurrentTimeMillis/1000;long currentSeconds=totalSeconds%60;long totalM inutes=totalSeconds/60;long currentMinutes=(totalSeconds%(60*60))/60;long currenthours=(totalMinutes/60)%24;System.out.print("输入时区偏移量：");byte zoneOffset=input.nextByte();long currentHour=(currenthours+(zoneOf fset*1))%24;System.out.println("当期时区的时间为："+currentHour+"时"+currentMinutes+"分"+currentSeconds+"秒");System.out.print("请输入v0,v1,t:");double v0=input.nextDouble();double v1=input.nextDouble();doublet=input.nextDouble();float a=(float)((v1-v0)/t);System.out.println("平均加速度a="+a);System.out.println("输入水的重量、初始温度、最终温度：");double water=input.nextDouble();double initialTemperature=input.nextDou ble();double finalTemperature=input.nextDouble();double Q=water*(finalTemp erature-initialTemperature)*4184;System.out.println("所需热量为："+Q);System.out.print("输入年数：");int numbers=input.nextInt();long oneYearsSecond=365*24*60*60;Longpop ulation=(long)((312032486+((oneYearsSecond/7.0)+(oneYearsSecond/45.0)-(oneYearsSecond/13.0))*numbers));System.out.println("第"+numbers+"年后人口总数为："+population);System.out.print("输入速度单位m/s和加速度a单位m/s2:");double v=input.nextDouble();double a1=input.nextDouble();double l engthOfAirplane=(Math.pow(v,2))/(2*a1);System.out.println("最短长度为："+lengthOfAirplane);System.out.print("输入存入的钱：");double money=input.nextInt();double monthRate=5.0/1200;for(int i=1;i<7; i++){double total=money*(Math.pow(1+monthRate,i));System.out.println("第"+i+"个月的钱为："+total);//告诉我书上的银行在哪里，我要去存钱，半年本金直接翻6倍、、、}System.out.print("用户请输入身高(英寸)、体重(磅):");double height=input.nextDouble();double weight=input.nextDouble(); double BMI=(weight*0.45359237)/(Math.pow((height*0.0254),2));System.out.println("BMI的值为"+BMI);System.out.print("输入x1和y1:");System.out.print("输入x2和y2:");double x1=input.nextDouble();double y1=input.nextDouble();double x2 =input.nextDouble();double y2=input.nextDouble();double point1=Math.pow((x2-x1),2);double point2=Math.pow((y2-y1),2);double distance=Math.pow((point1+point2),(1.0/2));//也可以Math.pow((point1+point2),0.5)System.out.println("两点间的距离为："+distance);System.out.print("输入六边形的边长：");double side=input.nextDouble();double area=(3*(Math.pow(3,0.5))*(Math.p ow(side,2)))/2;System.out.println("六边形的面积为："+area);}}。

public class xiti9{public static void main(String args[]) {int x=4;int y;if(x<1){y=x;}else if(x>=10){y=4*x;}else{y=3*x-2;}System.out.println("y="+y);}}习题12public class xiti12{public static void main(String args[]) {int sum=0;for(int k=1;k<=10;k++){sum=sum+k*k;}System.out.println("sum="+sum); }}习题13public class xiti13{public static void main(String args[]) {intt,a=3,b=5,c=8;if(a<b){t=a;a=b;b=t;}if(a<c){t=a;a=c;c=t;}{t=b;b=c;c=t;}System.out.println("大小顺序输出为："+a+" "+b+" "+c); }}习题14public class xiti14{public static void main(String args[]){int n=1;System.out.print("\n1-100之间的所有素数为：\n"+" 3"); for(int i=1;i<=100;i++){for(int j=2;j<=i/2;j++){if(i%j==0){break;}if(j==i/2){System.out.print(" "+i);n++;}}}System.out.println("\n共有"+n+"个素数。

j a v a语言程序设计基础篇第十版练习答案精编Document number：WTT-LKK-GBB-08921-EIGG-2298601import class Exercise14_01 extendsApplication {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}02import class Exercise14_02 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}03import class Exercise14_03 extends Application {@Override One is to use the hint in the book.ArrayList<Integer> list = new ArrayList<>(); for (int i = 1; i <= 52; i++) {(i);}HBox pane = new HBox(5);;().add(new ImageView("image/card/" + (0) +".png"));().add(new ImageView("image/card/" + (1) +".png"));().add(new ImageView("image/card/" + (2) +".png"));Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}04import class Exercise14_04 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}05import class Exercise14_05 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}05import class Exercise14_05 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}06import class Exercise14_06 extends Application {@Override dd(rectangle);}}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}07import class Exercise14_07 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}08import class Exercise14_08 extends Application {@Override ng"), j, i);}}Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}09import class Exercise14_09 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}class FanPane extends Pane {double radius = 50;public FanPane() {Circle circle = new Circle(60, 60, radius);;;getChildren().add(circle);Arc arc1 = new Arc(60, 60, 40, 40, 30, 35);; ddAll(arc1, arc2, arc3, arc4);}}10import class Exercise14_10 extends Application {@Override ddAll, ;Arc arc2 = new Arc(100, 140, 50, 20, 180, 180); ;;().addAll(ellipse, arc1, arc2,new Line(50, 40, 50, 140), new Line(150, 40, 150, 140));Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}11import class Exercise14_11 extends Application {@Override ddAll(circle, ellipse1, ellipse2,circle1, circle2, line1, line2, line3, arc);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}12import class Exercise14_12 extends Application {@Override ddAll(r1, text1, r2, text2, r3, text3, r4, text4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}13import class Exercise14_13 extends Application {@Override ddAll(arc1, text1, arc2, text2, arc3, text3, arc4, text4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}14import class Exercise14_14 extends Application {@Override ddAll(r1, r2, line1, line2, line3, line4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}15import class Exercise14_15 extends Application {@Override ddAll(polygon, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}16import class Exercise14_16 extends Application {@Override ind().divide(3));().bind());().bind().divide(3));;Line line2 = new Line(0, 0, 0, 0);().bind().multiply(2).divide(3));().bind());().bind().multiply(2).divide(3));;Line line3 = new Line(0, 0, 0, 0);().bind().divide(3));().bind().divide(3));().bind());;Line line4 = new Line(0, 0, 0, 0);().bind().multiply(2).divide(3));().bind().multiply(2).divide(3));().bind());;().addAll(line1, line2, line3, line4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}17import class Exercise14_17 extends Application {@Override ddAll(arc, line1, line2, line3, circle, line4, line5, line6, line7, line8);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}18import class Exercise14_18 extends Application {@Override ddAll(polyline, line1, line2,line3, line4, line5, line6, text1, text2);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}19import class Exercise14_19 extends Application {@Override ddAll(polyline1, polyline2, line1,line2,line3, line4, line5, line6, text1, text2,text3,text4, text5, text6, text7);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}20import class Exercise14_20 extends Application {@Override dd(new Line(x1, y1, x2, y2));dd(new Line(x2, y2, (x2 + (arctan + set45) * arrlen)),((y2)) + (arctan + set45) * arrlen)));().add(new Line(x2, y2, (x2 + (arctan - set45) * arrlen)),((y2)) + (arctan - set45) * arrlen)));}/*** The main method is only needed for the IDE with limited* JavaFX support. Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}21import class Exercise14_21 extends Application {@Override istance(x2, y2) + "");().addAll(circle1, circle2, line, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}22import class Exercise14_22 extends Application {@Override ddAll(circle1, circle2, line, text1, text2);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}23import class Exercise14_23 extends Application {@Override ddAll(r1, r2, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}24import class Exercise14_24 extends Application {@Override ddAll(polygon, new Circle(x5, y5, 10), text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}25import class Exercise14_25 extends Application {@Override ddAll(circle, polygon);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}26import class Exercise14_26 extends Application {@Override ddAll(clock1, clock2);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}27import class Exercise14_27 extends Application {@OverrideNot needed for running from the command line. */public static void main(String[] args) {launch(args);}}class DetailedClockPane extends Pane {private int hour;private int minute;private int second;lear();getChildren().addAll(circle, sLine, mLine, hLine);dd(new Line(xOuter, yOuter, xInner, yInner));}dd(text);}}}28import class Exercise14_28 extends Application {@OverrideNot needed for running from the command line.*/public static void main(String[] args) {launch(args);}}class ClockPaneWithBooleanProperties extends Pane { private int hour;private int minute;private int second;private boolean hourHandVisible = true;private boolean minuteHandVisible = true; private boolean secondHandVisible = true;public boolean isHourHandVisible() {return hourHandVisible;}public void setHourHandVisible(boolean hourHandVisible) {= hourHandVisible;paintClock();}public boolean isMinuteHandVisible() {return minuteHandVisible;}public void setMinuteHandVisible(boolean minuteHandVisible) {= minuteHandVisible;paintClock();}public boolean isSecondHandVisible() {return secondHandVisible;public void setSecondHandVisible(boolean secondHandVisible) {= secondHandVisible;paintClock();}lear();getChildren().addAll(circle, t1, t2, t3, t4);if (secondHandVisible) {getChildren().add(sLine);}if (minuteHandVisible) {getChildren().add(mLine);}if (hourHandVisible) {getChildren().add(hLine);}}}import class Exercise14_29 extends Application {final static double HGAP = 20;final static double VGAP = 20;final static double RADIUS = 5;final static double LENGTH_OF_SLOTS = 40;final static double LENGTH_OF_OPENNING = 15;final static double Y_FOR_FIRST_NAIL = 50;final static double NUMBER_OF_SLOTS = 9;final static double NUMBER_OF_ROWS =NUMBER_OF_SLOTS - 2;@Override dd(c);}}dd(new Line(x, y, x, y + LENGTH_OF_SLOTS)); }dd(new Line(centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 - HGAP,y + LENGTH_OF_SLOTS, centerX -(NUMBER_OF_ROWS - 1) * HGAP / 2 + NUMBER_OF_ROWS * HGAP,y + LENGTH_OF_SLOTS));dd(new Line(centerX + HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 + NUMBER_OF_ROWS * HGAP, y));().add(new Line(centerX - HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 - HGAP, y));dd(new Line(centerX - HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - HGAP / 2, Y_FOR_FIRST_NAIL - LENGTH_OF_OPENNING));().add(new Line(centerX + HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX + HGAP / 2, Y_FOR_FIRST_NAIL - LENGTH_OF_OPENNING));Not needed for running from the command line.*/public static void main(String[] args) { launch(args);}}。

java第二章练习题答案Java第二章练习题答案Java作为一种广泛应用的编程语言，具有着强大的功能和丰富的库。

学习Java 的过程中，练习题是巩固知识和提高编程能力的重要一环。

在第二章的练习题中，我们将探索一些基本的Java概念和语法。

下面是第二章练习题的答案，希望对大家的学习有所帮助。

1. 问题：什么是Java的标识符？标识符的命名规则是什么？答案：Java的标识符是用来标识变量、方法、类等的名称。

标识符的命名规则如下：- 必须以字母、下划线或美元符号开头；- 可以包含字母、数字、下划线或美元符号；- 大小写敏感；- 不能使用Java的关键字。

2. 问题：Java的八种基本数据类型是什么？答案：Java的八种基本数据类型分别是：- byte：字节型；- short：短整型；- int：整型；- long：长整型；- float：单精度浮点型；- double：双精度浮点型；- char：字符型；- boolean：布尔型。

3. 问题：如何声明一个整型变量并赋初值为10？答案：可以使用以下语句声明一个整型变量并赋初值为10：int num = 10;4. 问题：如何将一个字符串转换为整型？答案：可以使用Integer类的parseInt()方法将一个字符串转换为整型。

示例代码如下：String str = "123";int num = Integer.parseInt(str);5. 问题：如何声明一个常量？答案：可以使用关键字final来声明一个常量。

示例代码如下：final int MAX_NUM = 100;6. 问题：如何使用if-else语句实现条件判断？答案：可以使用if-else语句实现条件判断。

示例代码如下：int num = 10;if (num > 0) {System.out.println("num是正数");} else {System.out.println("num是负数或零");}7. 问题：如何使用for循环实现重复执行某段代码？答案：可以使用for循环实现重复执行某段代码。

Java语言程序设计 (郑莉 )第二章习题答案1.什么是对象、类，它们之间的联系答：1）对象是包含现实世界物体特征的抽象实体，它反映系统为之保存信息和与它交互的能力。

对象是一些属性及服务的封装体，在程序设计领域，可以用“对象=数据+作用于这些数据上的操作”来表示。

现实生活中对象是指客观世界的实体；在程序中对象是指一组变量和相关方法的集合。

2）类是既有相同操作功能和相同的数据格式的对象的集合与抽象！3）两者的关系：对象是类的具体实例. 。

2.什么是面向对象的程序设计方法它有那些基本特征答：面向对象程序设计从所处理的数据入手，以数据为中心而不是以服务为中心来描述系统。

它把编程问题视为一个数据集合，数据相对于功能而言，具有更强的稳定性。

它的特征：抽象，封装，继承，多态。

3（无用）4．请解释类属性、实例属性及其区别。

答：实例属性，由一个个的实例用来存储所有实例都需要的属性信息，不同实例的属性值可能会不同。

5．请解释类方法、实例属性及其区别。

答：实例方法表示特定对象的行为，在声明时前面不加static修饰符，在使用时需要发送给一个类实例。

类方法也称为静态方法，在方法声明时前面需加static修饰符，类方法表示具体实例中类对象的共有行为。

区别：实例方法可以直接访问实例变量，调用实例方法，实例方法可以直接访问类变量，调用类方法；类方法可以直接调用类变量和类方法，类方法不能直接调用实例变量和实例方法；6．类的访问控制符有哪几种具体含义及其区别。

答：类的访问控制符只有public （公共类）及无修饰符（默认类）两种。

区别：当使用 public修饰符时表示所有其他的类都可以使用此类；当没有修饰符时，则只有与此类处于同一包中的其他类可以使用类。

7类成员的访问控制符有哪几种他们对类成员分别有哪些访问限制的作用答 : 类成员的访问控制符有public,private,protecte及无修饰符.public( 公有的 ): 用 public修饰的成分表示公有的, 也就是它可以被其他任何对象访问( 前提是对累成员所在的类访问有访问权限).Private(保护的 ) ：类中限定为private的成员只能被这个类本身访问，在类外不可见。

Java语言程序设计课后习题答案全集Java语言程序设计是一门广泛应用于软件开发领域的编程语言，随着其应用范围的不断扩大，对于掌握Java编程技巧的需求也逐渐增加。

为了帮助读者更好地掌握Java编程，本文将提供Java语言程序设计课后习题的全集答案，供读者参考。

一、基础知识题1. 代码中的注释是什么作用？如何使用注释.答：注释在代码中是用来解释或者说明代码的功能或用途的语句，编译器在编译代码时会自动忽略注释。

在Java中，有三种注释的方式：- 单行注释：使用"// " 可以在代码的一行中加入注释。

- 多行注释：使用"/* */" 可以在多行中添加注释。

- 文档注释：使用"/** */" 可以添加方法或类的文档注释。

2. 什么是Java的数据类型？请列举常见的数据类型。

答：Java的数据类型用来指定变量的类型，常见的数据类型有：- 基本数据类型：包括整型（byte、short、int、long）、浮点型（float、double）、字符型（char）、布尔型（boolean）。

- 引用数据类型：包括类（class）、接口（interface）、数组（array）等。

二、代码编写题1. 编写Java程序，输入两个整数，求和并输出结果。

答：```javaimport java.util.Scanner;public class SumCalculator {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.print("请输入第一个整数：");int num1 = scanner.nextInt();System.out.print("请输入第二个整数：");int num2 = scanner.nextInt();int sum = num1 + num2;System.out.println("两个整数的和为：" + sum);}}```三、综合应用题1. 编写Java程序，实现学生信息管理系统，要求包括以下功能：- 添加学生信息（姓名、年龄、性别、学号等）；- 修改学生信息；- 删除学生信息；- 查询学生信息。

《Java程序设计》课后习题参考答案Java程序设计课后习题参考答案1. 介绍在 Java 程序设计课程中，课后习题是帮助学生巩固知识、加深理解和提高编程能力的重要环节。

本文将为大家提供《Java程序设计》课后习题的参考答案，以帮助学生更好地学习和掌握 Java 编程。

2. 基本概念Java 程序设计课后习题涵盖了从基础到高级的各种知识点，包括但不限于变量、数据类型、条件语句、循环语句、数组、类、对象、继承、多态等内容。

通过解答这些习题，学生可以加深对这些概念的理解，并且通过实际操作来巩固他们的编程能力。

3. 习题解答策略当解答课后习题时，以下几个策略可以帮助你更好地理解和解决问题：3.1 仔细阅读题目要求。

确保自己充分理解题目所要求的功能和目标。

3.2 分析问题。

在着手解答问题之前，先理清思路，分析问题的要点和关键部分。

3.3 设计算法。

根据问题的要求，设计一个合适的算法来解决问题。

3.4 编写代码。

用 Java 编程语言将你设计的算法转化为代码实现。

3.5 测试和调试。

对编写的代码进行测试和调试，确保程序能够正常运行，并且得到正确的结果。

4. 习题参考答案示例下面我们将列举几个常见的习题参考答案示例，以帮助大家更好地理解和学习 Java 程序设计：4.1 变量与数据类型：习题要求定义一个整型变量并赋值为10，然后输出该变量的值。

```public class VariableExample {public static void main(String[] args) {int num = 10;System.out.println("变量的值为：" + num);}}```4.2 条件语句：习题要求判断一个数是否是偶数，如果是，则输出“偶数”，否则输出“奇数”。

```public class EvenOddExample {public static void main(String[] args) {int num = 5;if (num % 2 == 0) {System.out.println("偶数");} else {System.out.println("奇数");}}}```4.3 循环语句：习题要求输出1到10之间的所有偶数。

《Java语言程序设计（基础篇）》（第10版梁勇著）第二十一章练习题答案21.1import java.util.*;public class Exercise21_01 {public static void main(String[] args) {LinkedHashSet<String> set1 = new LinkedHashSet<String>(Arrays.asList( new String[]{"George", "Jim", "John", "Blake", "Kevin", "Michael"}));LinkedHashSet<String> set1Clone1 = (LinkedHashSet<String>)set1.clone(); LinkedHashSet<String> set1Clone2 = (LinkedHashSet<String>)set1.clone();LinkedHashSet<String> set2 = new LinkedHashSet<String>(Arrays.asList( new String[] {"George", "Katie", "Kevin", "Michelle", "Ryan"}));set1.addAll(set2);set1Clone1.removeAll(set2);set1Clone2.retainAll(set2);System.out.println("The union of the two sets is " + set1);System.out.println("The difference of the two sets is " + set1Clone1); System.out.println("The intersection of the two sets is " + set1Clone2); }}21.1附加import java.util.*;public class Exercise21_01Extra {public static void main(String[] args) {System.out.print("Enter a string: ");Scanner input = new Scanner(System.in);String s = input.nextLine();Character[] list1 = {'A', 'E', 'I', 'O', 'U'};Set<Character> vowels = new HashSet<>(Arrays.asList(list1));Set<Character> vowelsInString = new HashSet<>();Set<Character> consonantsInString = new HashSet<>();int numbeOfVowels = 0;int numbeOfConsonants = 0;for (int i = 0; i < s.length(); i++) {char ch = Character.toUpperCase(s.charAt(i));if (Character.isLetter(ch)) {if (vowels.contains(ch)) {if (!vowelsInString.contains(ch)) {vowelsInString.add(ch);numbeOfVowels++;}}else if (!consonantsInString.contains(ch)) {consonantsInString.add(ch);numbeOfConsonants++;}}}System.out.println("The number of vowels is " + numbeOfVowels);System.out.println("The number of consonants is " + numbeOfConsonants); }}21.2import java.util.*;import java.io.*;public class Exercise21_02 {public static void main(String[] args) {if (args.length != 1) {System.out.println("Usage: java Exercise21_02 fullfilename");System.exit(1);}String filename = args[0];// Create a tree set to hold the wordsTreeSet<String> treeSet = new TreeSet<String>();try {Scanner in = new Scanner(new File(filename));String line;while ((line = in.nextLine()) != null) {String[] tokens = line.split("[ |\n|\t|\r|.|,|)|(|-|\"]");for (int i = 0; i < tokens.length; i++)treeSet.add(tokens[i]);}}catch (Exception ex) {System.err.println(ex);}// Get an iterator for the setIterator iterator = treeSet.iterator();// Display mappingsSystem.out.println("\nDisplay words in ascending order ");while (iterator.hasNext()) {System.out.println(iterator.next());}}}21.3import java.util.*;import java.io.*;public class Exercise21_03 {public static void main(String[] args) {// Check usageif (args.length != 1) {System.out.println("Usage: java Exercise21_03 file.java");System.exit(1);}// Array of all Java keywords + true + nullString[] keywordString = {"abstract", "finally", "public", "boolean", "float", "return", "break", "for", "short", "byte","goto", "static", "case", "if", "super", "catch", "implements", "switch", "char", "import", "synchronized", "class","instanceof", "this", "const", "int", "throw", "continue","interface", "throws", "default", "long", "transient", "do","native", "try", "double", "new", "void", "else", "package","volatile", "extends", "private", "while", "final","protected", "true", "null"};Set<String> keywordSet =new HashSet<String>(Arrays.asList(keywordString));int count = 0;try {Scanner input = new Scanner(new File(args[0]));String text = "";while (input.hasNext()) {String line = input.nextLine();line = stripLineComments(line);line = stripLineStringLiterals(line);text += line + " ";}text = stripParagraghComments(text);String[] tokens = text.split("[ \\[,()\\]]");for (String token: tokens) {if (keywordSet.contains(token))count++;}System.out.println("The number of keywords in the program is " + count);}catch (Exception ex) {ex.printStackTrace();}}/* Strip line comments */private static String stripLineComments(String line) {int index = line.indexOf("//");if (index < 0)return line;elsereturn line.substring(0, index);}/* Strip string literals */private static String stripLineStringLiterals(String line) {int start = line.indexOf("\"");int end = line.indexOf("\"", start + 1);while (start > 0 && end > 0) {line = line.substring(0, start) + line.substring(end + 1);start = line.indexOf("\"");end = line.indexOf("\"");}return line;}/* Strip paragraph comments */private static String stripParagraghComments(String text) {int start = text.indexOf("/*");int end = text.indexOf("*/");while (start > 0 && end > 0) {text = text.substring(0, start) + text.substring(end + 2);start = text.indexOf("/*");end = text.indexOf("*/");}return text;}}/** This is an incorrect version. It does not count the case such as (this. Here the this keyword* is not counted. It does not exclude keywords in the comments*import java.util.*;import java.io.*;public class Exercise20_03 {public static void main(String[] args) {// Check usageif (args.length != 1) {System.out.println("Usage: java Exercise20_03 file.java");System.exit(0);}// Array of all Java keywords + true + nullString[] keywordString = {"abstract", "finally", "public","boolean", "float", "return", "break", "for", "short", "byte", "goto", "static", "case", "if", "super", "catch", "implements", "switch", "char", "import", "synchronized", "class","instanceof", "this", "const", "int", "throw", "continue","interface", "throws", "default", "long", "transient", "do","native", "try", "double", "new", "void", "else", "package","volatile", "extends", "private", "while", "final","protected", "true", "null"};Set<String> keywordSet =new HashSet<String>(Arrays.asList(keywordString));int count = 0;try {Scanner input = new Scanner(new File(args[0]));while (input.hasNext()) {String token = input.next();if (keywordSet.contains(token))count++;}System.out.println("The number of keywords in the program is " + count);}catch (Exception ex) {ex.printStackTrace();}}}*/21.4import java.util.Scanner;import java.util.HashSet;import java.util.Arrays;public class Exercise21_04 {public static void main(String[] args) throws Exception {HashSet<Character> set1 = new HashSet<Character>(Arrays.asList( new Character[]{'A', 'E', 'I', 'O', 'U'}));System.out.print("Enter a filename: ");Scanner input = new Scanner(System.in);String filename = input.nextLine();input = new Scanner(new java.io.File(filename));int countVowels = 0;int countConsonants = 0;while (input.hasNext()) {String s = input.nextLine().toUpperCase();for (int i = 0; i < s.length(); i++) {if (set1.contains(s.charAt(i)))countVowels++;else if (Character.isLetter(s.charAt(i)))countConsonants++;}}System.out.println("The number of vowels is " + countVowels + " and consonanats is " +countConsonants);}}21.5/*** Usage: Copy this class to the folder, run it with java JavaToHTMLftim * to generate* HTM file for all the .java file in this folder. The generated .htm files are* stored in the same folder*/import java.util.*;import java.io.*;public class Exercise21_05 {// Array of all Java keywords + true + false + nullstatic String[] keywordString = {"abstract", "assert", "boolean","break", "byte", "case", "catch", "char", "class", "const","continue", "default", "do", "double", "else", "enum","extends", "for", "final", "finally", "float", "goto", "if","implements", "import", "instanceof", "int", "interface","long", "native", "new", "package", "private", "protected","public", "return", "short", "static", "strictfp", "super","switch", "synchronized", "this", "throw", "throws","transient", "try", "void", "volatile", "while","true", "false", "null"};static Set<String> keywordSet =new HashSet<String>(Arrays.asList(keywordString));/** Main method */public static void main(String[] args) throws Exception {// Check usageif (args.length != 2) {System.out.println("Usage: java Exercise20_10 javaSourcefile htmlfile");System.exit(1);}Scanner input = new Scanner(new File(args[0]));PrintWriter output = new PrintWriter(new File(args[1]));JavaToHTML(input, output);}static boolean stringToken = false;static String inputFileName;public static void JavaToHTML(Scanner input, PrintWriter output) { try {output.format("%s\r\n", "<html>");output.format("%s\r\n", "<head>");output.format("%s\r\n","<title>Intro to Java Programming, 6E - " + inputFileName +"</title>");output.format("%s\r\n","<meta http-equiv=\"Content-Type\" content=\"text/html; charset=windows-1252\">");output.format("%s\r\n", "<style type = \"text/css\">");output.format("%s\r\n","body {font-family: \"Courier New\", sans-serif; font-size: 100%; color: black}");output.format("%s\r\n",".keyword {color: #000080; font-weight: bold}");output.format("%s\r\n", ".comment {color: #008000}");output.format("%s\r\n", ".literal {color: #0000ff}");// Match the color in the text// output.format("%s\r\n", ".keyword {color: black; font-weight: bold}");// output.format("%s\r\n", ".comment {color: #77797C}");// output.format("%s\r\n", ".literal {color: #007346; font-weight: bold}");output.format("%s\r\n", "</style>");output.format("%s\r\n", "</head>");output.format("%s\r\n", "<body>");output.format("%s\r\n", "<pre>");String text = "";String temp;// Read all lineswhile (input.hasNext()) {temp = input.nextLine();text += temp + "\r\n";}text = text.replaceAll(">", "&gt;");text = text.replaceAll("<", "&lt;");translateToHTML(text, input, output);output.format("%s\r\n", "</pre>");output.format("%s\r\n", "</body>");output.format("%s\r\n", "</html>");}catch (Exception ex) {System.out.println(ex);}finally {try {input.close();output.close();}catch (Exception ex) {}}}/** Translate Java source code to HTML */static void translateToHTML(String text, Scanner input, PrintWriter output) throws Exception {text = text.replaceAll("// ", "LINECOMMENT");text = text.replaceAll("/\\*", "BLOCKCOMMENT");String token;while (text != null && text.length() > 0) {// * and / are in conflict with /* and //String[] parts = text.split("[%\\+\\-\\*/\r\n\t \\[\\].;(){},]", 2); token = parts[0];if (token.length() > 1 && token.startsWith("LINECOMMENT")) {output.format("%s", "<span class = \"comment\">");parts = text.split("\r\n", 2);text = parts[1];output.format("%s", parts[0].replaceAll("LINECOMMENT", "// "));output.format("%s", "</span>\r\n");continue;}else if (token.length() > 1 && token.startsWith("BLOCKCOMMENT")) {output.format("%s", "<span class = \"comment\">");parts = text.split("\\*/", 2);text = parts[1];output.format("%s", parts[0].replaceAll("BLOCKCOMMENT", "/*") +"*/");output.format("%s", "</span>");continue;}else if (token.length() > 1 && token.matches("'\\w'*")) {output.format("%s", "<span class = \"literal\">");output.format("%s", token);output.format("%s", "</span>");}else if (token.startsWith("\"") && token.endsWith("\"") &&(token.length() > 1)) {output.format("%s", "<span class = \"literal\">" + token+ "</span>");}else if (token.startsWith("'") && token.endsWith("'") &&(token.length() > 1)) {output.format("%s", "<span class = \"literal\">" + token+ "</span>");}else if (token.equals("' '")) {output.format("%s", "<span class = \"literal\">" + token+ "</span>");}else if (token.startsWith("\"") && token.endsWith("\"") &&(token.length() == 1)) {if (stringToken) {output.format("%s", token + "</span>");stringToken = false;}else {output.format("%s", "<span class = \"literal\">" + token); stringToken = true;}}else if (token.startsWith("\"")) {output.format("%s", "<span class = \"literal\">" + token); stringToken = true;}else if (token.endsWith("\"") && (!token.endsWith("\\\""))) { output.format("%s", token);output.format("%s", "</span>");stringToken = false;}else if (token.matches("\\d+")) { // Check if numericoutput.format("%s", "<span class = \"literal\">" + token +"</span>");}else if (!stringToken && keywordSet.contains(token)) {output.format("%s", "<span class = \"keyword\">" + token +"</span>");}else {output.format("%s", token);}if (token.length() < text.length()) {if (text.charAt(token.length()) == '<')output.format("%s", "&lt;");else if (text.charAt(token.length()) == '>')output.format("%s", "&gt;");elseoutput.format("%s", text.charAt(token.length()));}if (parts.length == 2) {text = parts[1];}}}}21.6import java.util.*;public class Exercise21_06 {public static void main(String[] args) {// Create a tree map to hold words and key and count as value TreeMap<Integer, Integer> treeMap = new TreeMap<>();Scanner input = new Scanner(System.in);while (true) {// Enter an integerSystem.out.print("Enter an integer: ");int number = input.nextInt();if (number == 0) break;Integer key = new Integer(number);if (treeMap.get(key) != null) {int value = ((Integer)treeMap.get(key)).intValue();value++;treeMap.put(key, new Integer(value));}else {treeMap.put(key, new Integer(1));}}Integer max = Collections.max(treeMap.values());Set<Integer> keys = treeMap.keySet();Iterator<Integer> iterator = keys.iterator();while (iterator.hasNext()) {Object key = iterator.next();Integer value = (Integer)(treeMap.get(key));if (value.equals(max)) {System.out.println("Number " + key + " occurred most");}}}}21.7import java.util.*;public class Exercise21_07 {public static void main(String[] args) {// Text in a stringString text = "Have a good day. Have a good class. " + "Have a good visit. Have fun!";// Create a hash map to hold words and key and count as value HashMap<String, Integer> hashMap = new HashMap<>();String[] tokens = text.split("[ |.|!|?]");for (String key: tokens) {if (hashMap.get(key) != null) {hashMap.put(key, hashMap.get(key).intValue() + 1);}else {if (key.trim().length() > 0)hashMap.put(key, 1);}}// Get an entry set for the tree mapSet<Map.Entry<String, Integer>> entrySet = hashMap.entrySet();ArrayList<WordOccurrence> list = new ArrayList<>();for (Map.Entry<String, Integer> entry: entrySet) {list.add(new WordOccurrence(entry.getKey(), entry.getValue())); }Collections.sort(list);for (WordOccurrence item: list) {System.out.println(item);}}}class WordOccurrence implements Comparable<WordOccurrence> {String word;int count;public WordOccurrence(String word, int count) {this.word = word;this.count = count;}@Overridepublic int compareTo(WordOccurrence o) {return count - o.count;}@Overridepublic boolean equals(Object o) {return word.equals(((WordOccurrence)o).word);}@Overridepublic String toString() {return word + ": " + count;}}21.8import java.util.*;import java.io.*;public class Exercise21_08 {public static void main(String[] args) {if (args.length != 1) {System.out.println("Usage: java Exercise21_08 fullfilename");System.exit(1);}String filename = args[0];// Create a tree map to hold words as key and count as valueTreeMap<String, Integer> treeMap = new TreeMap<String, Integer>();try {Scanner input = new Scanner(new File(filename));while (input.hasNext()) {String line = input.nextLine();String[] words = line.split("[ @!~{}\\[\\]$#^&*\n\t\r.,;?'\")(]");for (int i = 0; i < words.length; i++) {if (words[i].trim().length() > 0 &&words[i].trim().matches("[A-Z|a-z]+")) {String key = words[i].toLowerCase();if (treeMap.get(key) != null) {int count = treeMap.get(key);count++;treeMap.put(key, count);}else {treeMap.put(key, 1);}}}}}catch (Exception ex) {ex.printStackTrace();}// Get an entry set for the tree mapSet<Map.Entry<String, Integer>> entrySet = treeMap.entrySet();// Display words in alphabetical orderSystem.out.println("\nDisplay words and their count in " + " ascending order of the words");for (Map.Entry<String, Integer> entry: entrySet)System.out.println(entry.getValue() + "\t" + entry.getKey()); }}21.9import java.util.*;public class Exercise21_09 {public static void main(String[] args) {String[][] stateCapital = {{"Alabama", "Montgomery"},{"Alaska", "Juneau"},{"Arizona", "Phoenix"},{"Arkansas", "Little Rock"},{"California", "Sacramento"},{"Colorado", "Denver"},{"Connecticut", "Hartford"},{"Delaware", "Dover"},{"Florida", "Tallahassee"},{"Georgia", "Atlanta"},{"Hawaii", "Honolulu"},{"Idaho", "Boise"},{"Illinois", "Springfield"},{"Indiana", "Indianapolis"},{"Iowa", "Des Moines"},{"Kansas", "Topeka"},{"Kentucky", "Frankfort"},{"Louisiana", "Baton Rouge"},{"Maine", "Augusta"},{"Maryland", "Annapolis"},{"Massachusettes", "Boston"},{"Michigan", "Lansing"},{"Minnesota", "Saint Paul"},{"Mississippi", "Jackson"},{"Missouri", "Jefferson City"},{"Montana", "Helena"},{"Nebraska", "Lincoln"},{"Nevada", "Carson City"},{"New Hampshire", "Concord"},{"New Jersey", "Trenton"},{"New York", "Albany"},{"New Mexico", "Santa Fe"},{"North Carolina", "Raleigh"},{"North Dakota", "Bismark"},{"Ohio", "Columbus"},{"Oklahoma", "Oklahoma City"},{"Oregon", "Salem"},{"Pennslyvania", "Harrisburg"},{"Rhode Island", "Providence"},{"South Carolina", "Columbia"},{"South Dakota", "Pierre"},{"Tennessee", "Nashville"},{"Texas", "Austin"},{"Utah", "Salt Lake City"},{"Vermont", "Montpelier"},{"Virginia", "Richmond"},{"Washington", "Olympia"},{"West Virginia", "Charleston"},{"Wisconsin", "Madison"},{"Wyoming", "Cheyenne"}};Map<String, String> map = new HashMap<String, String>();for (int i = 0; i < stateCapital.length; i++)map.put(stateCapital[i][0].toLowerCase(), stateCapital[i][1]);Scanner input = new Scanner(System.in);System.out.print("Enter a state: ");String state = input.nextLine().toLowerCase().trim();if (map.containsKey(state))System.out.println("The capital is " +map.get(state));elseSystem.out.println("No such state ");}}21.10import java.util.*;import java.io.*;public class Exercise21_10 {public static void main(String[] args) {// Prompt the user to enter a Java source fileScanner input = new Scanner(System.in);System.out.print("Enter a file name: ");String filename = input.nextLine();// Array of all Java keywords + true + nullString[] keywordString = { "abstract", "finally", "public", "boolean", "float", "return", "break", "for", "short", "byte", "goto", "static","case", "if", "super", "catch", "implements", "switch", "char","import", "synchronized", "class", "instanceof", "this", "const","int", "throw", "continue", "interface", "throws", "default", "long","transient", "do", "native", "try", "double", "new", "void", "else","package", "volatile", "extends", "private", "while", "final","protected", "true", "null" };Set<String> keywordSet = newHashSet<String>(Arrays.asList(keywordString));int count = 0;try {input = new Scanner(new File(filename));String text = "";while (input.hasNext()) {String line = input.nextLine();line = stripLineComments(line);line = stripLineStringLiterals(line);text += line + " ";}text = stripParagraghComments(text);TreeMap<String, Integer> map = new TreeMap<String, Integer>();String[] tokens = text.split("[ \\[,()\\]]");for (String token : tokens) {if (keywordSet.contains(token))if (map.get(token) == null) {map.put(token, 1);} else {int value = map.get(token);value++;map.put(token, value);}}// Get all entries into a setSet<Map.Entry<String, Integer>> entrySet = map.entrySet();// Get key and value from each entryfor (Map.Entry<String, Integer> entry: entrySet)System.out.println(entry.getValue() + "\t" + entry.getKey()); } catch (Exception ex) {ex.printStackTrace();}}/* Strip line comments */private static String stripLineComments(String line) {int index = line.indexOf("//");if (index < 0)return line;elsereturn line.substring(0, index);}/* Strip string literals */private static String stripLineStringLiterals(String line) {int start = line.indexOf("\"");int end = line.indexOf("\"", start + 1);while (start > 0 && end > 0) {line = line.substring(0, start) + line.substring(end + 1);start = line.indexOf("\"");end = line.indexOf("\"");}return line;}/* Strip paragraph comments */private static String stripParagraghComments(String text) {int start = text.indexOf("/*");int end = text.indexOf("*/");while (start > 0 && end > 0) {text = text.substring(0, start) + text.substring(end + 2);start = text.indexOf("/*");。