java2简明教程部分课后复习题答案

JAVA2简明教程习题答案第二章课堂习题:public class Main{public static void main(String[] args) {//initialization phase初始段float f1 = 2.5f;float f2;int a = 7;int b = 2;int c;//processing phase 处理段f2 = f1 + (a/b);c = (a/b);//termination phase终止段System.out.println("f2的值为: " + f2);System.out.println("c的值为: " + c);}}课后习题:2-4(小程序部分)import java.applet.*;import java.awt.*;public class Gess extends Applet{public void paint(Graphics g){//3~10000中的任意数int m = 20;int n = 9993;g.drawString("本程序仅对3~10000中任意取的整数: ",80,50);g.drawString("20" ,80,65);g.drawString("9993" ,80,80);g.drawString("进行测试! " ,80,95);while (m !=1) //假设最后得到的数一定是1,则如果不为1就换算{if (m %2 == 0) //如果被2整除则为偶数,除以2m = m /2;else //如果不被2整除则为奇数,乘以3再加1 {m = m *3 + 1;}}while (n !=1) //假设最后得到的数一定是1,则如果不为1就换算{if (n %2 == 0) //如果被2整除则为偶数,除以2n = n /2;else //如果不被2整除则为奇数,乘以3再加1{n = n *3 + 1;}}g.drawString("20换算后的值为: " + m,80,110);g.drawString("9993换算后的值为: " + m,80,125);}}(程序部分)import java.io.*; //引入java.io中的所有类(含输入输出类),因为程序中要用到输入类的read()方法public class Main{public static void main(String[] args){byte []buf =new byte[50]; //50个字节的数组用于存字符串String str;long m = 0;System.out.println("请输入3~10000中的任意整数(回车确认):");try //try 语气{System.in.read(buf); //从键盘读入一数字串保存于buf 中str = new String(buf); //buf转换成字符串对象str m = Long.parseLong(str.trim()); //数字转换成整数}catch (Exception e){} //catch语气,Exception为异常类while (m !=1) //假设最后得到的数一定是1,则如果不为1就换算{if (m %2 == 0) //如果被2整除则为偶数,除以2m = m /2;else //如果不被2整除则为奇数,乘以3再加1{m = m *3 + 1;}}System.out.println("换算后的值为:\t" + m);}}1、EX_2.5import java.applet.Applet;import java.awt.*;public class compareNumbers extends Applet{Label l1, l2;TextField in1, in2;int a, b;public void init() {l1 = new Label("第一个整数：");l2 = new Label("第二个整数：");in1 = new TextField(8);in2 = new TextField(8);add(l1);add(in1);add(l2);add(in2);}public boolean action(Event e, Object o) {if(e.target==in1||e.target==in2){a = Integer.parseInt(in1.getText());b = Integer.parseInt(in2.getText());if (a == b) {showStatus("the two numbers are equal!");} else if (a > b) {showStatus(a + " is larger!");} elseshowStatus(b + " is larger!");}return true;}}2-6public class Main{public static void main(String[] args){// initialization phase //初始段int j = 1;int []a; //用于存放第一个骰子的点数的整形数组int []b; //用于存放第二个骰子的点数的整形数组int two = 0; //相加和为2的计数器int sev = 0; //相加和为7的计数器int twe = 0; //相加和为12的计数器int oth = 0; //相加和为其他数的计数器a = new int [6]; //分配数组空间b = a; //骰子的点数相同,这里将数组a赋给数组b(这时b和a同用一块内存空间)//processing phase 处理段for(int i = 0; i < 6; i++) //通过循环赋值方式初始化数组{a[i] = j++;}for(int i = 0; i < 3600; i++) //测试3600次{//生成0~5随机数int m = (int)(((Math.random())*6 ));int n = (int)(((Math.random())*6 ));if ((a[m] + b[n]) == 2) //当相加和为2时对应计数器加1two++;else if ((a[m] + b[n]) == 7) //当相加和为7时对应计数器加1sev++;else if((a[m] + b[n]) == 12) //当相加和为12时对应计数器加1twe++;else //当相加和为其他数时对应计数器加1 oth++;}//termination phase 终止段//输出结果//((float)two/3600)为将two/3600的结果强制转换成浮点数输出,否则输出为0 System.out.println("相加的和为 2 的次数是:\t" + two+ ";\t可能性为:\t" + ((float)two/3600));System.out.println("相加的和为 12 的次数是:\t" + twe+ ";\t可能性为:\t" + ((float)twe/3600));System.out.println("相加的和为 7 的次数是:\t"+ sev+ ";\t可能性为:\t" + ((float)sev/3600));System.out.println("相加的和为其他数的次数是:\t"+ oth + ";\t可能性为:\t" + ((float)oth/3600) );}}第三章课堂习题随机产生26个英文字母a-z,直到大于u为止,用while或for语气实现public class Main {public static void main(String[] args){int letter = 0;System.out.println("用 while 语句实现: ");while(letter < 'u'){letter = (int)(Math.random()*26) + 'a';System.out.println((char)letter);}System.out.println("用 for 语句实现: ");for(letter = 97; letter < 'u';letter++){letter = (int)(Math.random()*26) + 'a';System.out.println((char)letter);}}}课后习题3-1import java.applet.Applet;import java.awt.*;public class Display extends Applet{Label lab;TextField input;long num;long m = 0;long n = 0;int i = 0; //数字个数的计数器public void init(){lab = new Label("请输入任意整数:"); //提示标签input = new TextField(20); //输入文本框add(lab); //在网页中显示标签labadd(input); //在网页中显示文本框}public boolean action (Event e, Object o){if (e.target == input){num = Long.parseLong( input.getText() ); //字符串转换成整形//把得到的数倒置do{m = num%10; //求余得最后一个数字num = num/10; //取整去掉最后一个数字n = n*10 + m; //把倒置后的数存到n中i++; //同时计数器自加}while(num != 0);System.out.println("下面是得到的结果:" + i);//间隔加空格后输出do{System.out.print(" " + n%10);n = n/10;}while((i--) > 1);}return true;}}3-2public class Main {public static void main(String[] args){System.out.println("整数\t" + "平方\t" + "立方");//范围0~10for(int i = 0; i <= 10; i++){//依次打印输出整数,平方,立方System.out.println(i + "\t" + i*i + "\t" + i*i*i);}}}3-3public class Main{public static void main(String[] args){// 把图分成三部分左中右三部分打印for(int i = 0; i < 5;i++ ){//循环打印出左边部分for(int j = 0; j <= i;j++){System.out.print("*");}//循环打印出中间部分for(int k = 2*i; k < 18; k++) //空格要考虑前后各少一个所以从2*i 开始{System.out.print(" ");}//循环打印出右边部分for(int m = 0; m <= i;m++){System.out.print("*");}System.out.println();}System.out.println();}}3-4import java.applet.Applet;import java.awt.*;public class Rectangle extends Applet{Label lab;TextField input;int width; //矩形的长public void init(){lab = new Label("请输入矩形的长(整数):"); //请示标签 input = new TextField(20); //输入文本框add(lab); //在网页中显示标签labadd(input); //在网页中显示文本框}public boolean action(Event e, Object o){//当用户按下Enter时把输入的字符串转换成整形if (e.target == input)width = Integer.parseInt( input.getText() );System.out.println("下面是得到的矩形:");//矩形的上底for(int i = 0; i < width; i++){System.out.print("*");}//矩形的边for (int k = 0; k < width-2; k++){System.out.println();System.out.print("*");//矩形的中间为空for (int m = 0; m < width-2; m++) {System.out.print(" ");}System.out.print("*");}System.out.println();//矩形的下底for(int j = 0; j < width; j++){System.out.print("*");}return true;}}第四章4-1import java.io.*;public class ReverOrder{static int x;int num;int m;int n;//从键盘读入字符串public static String readString(){BufferedReader br = new BufferedReader( new InputStreamReader(System.in),1 );String string = "";try{string = br.readLine();}catch( IOException ex ){System.out.println(ex);}return string;}//将读入的字符串转换为整形public static int input(){System.out.print("请输入一串数字:\t");return Integer.parseInt(readString());}//倒序输入的字符串int Rorder(int b){num = b;{m = num%10; //求余得最后一个数字num = num/10; //取整去掉最后一个数字n = n*10 + m; //把倒置后的数存到n中}while( num != 0);return n;}//输出结果void show(int a){System.out.println("倒序输出为:\t" + a);}//主方法public static void main(String[] args){int value;ReverOrder order = new ReverOrder();x = ReverOrder.input(); //将输入的数传递给x value = order.Rorder(x); //将x倒置order.show(value); //输出}}4-3package homework4_3;import java.io.*;public class Circle{static double radius;double length;double area;static boolean checkr;//构造函数初始化半径public Circle(double r){if(r < 0)checkr = false;}else{radius = r;checkr = true;}}//从键盘读入字符串public static String readString(){BufferedReader br = new BufferedReader( new InputStreamReader(System.in),1 );String string = "";try{string = br.readLine();}catch( IOException ex ){System.out.println(ex);}return string;}//将读入的字符串转换为整形public static double input(){System.out.print("请输入圆的半径:\t");return Double.parseDouble(readString());}//计算圆的周长的方法void Length(double r){System.out.println("圆的周长为:\t" + Math.PI*r*2);}//计算圆的面积void Area(double r)System.out.println("圆的面积为:\t" + Math.PI*r*r);}//主方法public static void main(String[] args){double valueinput;double valuer;Circle r = new Circle(input());//如果半径为正则求周长和面积if(checkr){r.Area(radius);r.Length(radius);}elseSystem.out.println("输入圆的半径的值不能为负数!");}}4-4public class Date{static int year;static int month;static int day;public Date(){//无参数的构造函数}//有三个参数的构造函数public Date(int x, int y, int z){day = x;month = y;year = z;//主方法public static void main(String[] args){year = 2008;month = 06;day = 21;//(１)三种格式输出今天的日期System.out.print("今天是:" );System.out.println("\t" + year + " " + month + " " + day );System.out.println("\t" + month + " " + day + " " + year );System.out.println("\t" + day + " " + month + " " + year );//(2)调用重载构造函数创建对象dateDate date = new Date(22,06,2008);System.out.print("\n明天是:" );System.out.println("\t" + year + " " + month + " " + day );System.out.println("\t" + month + " " + day + " " + year );System.out.println("\t" + day + " " + month + " " + year ); }}4-6//基类class base{//方法一void First(){System.out.println("这是基类base的第一个方法!");Second();}//方法二void Second(){System.out.println("这是基类base的第二个方法!");}}//派生类class derived extends base{void Second(){System.out.println("这是派生类derived的方法!");}}public class UpCasting{//主方法public static void main(String[] args){//派生类derived对象test,test对象里有覆盖了基类的Second()方法的Second()方法derived test = new derived();base up = test; //向上类型转换, 基类对象up里有有First()方法和被覆盖的Second()//base up = new base(); //基类对象up里仅有First()方法和未被覆盖的Second()up.First(); //调用基类的第一个方法}}第6章、Ex_6.6import java.util.*;public class Text {public void countYYZM(String text) {int i = 0;int countA = 0, countE = 0, countI = 0, countO = 0, countU = 0;while (i < text.length()) {switch (text.charAt(i)) {case 'a':case 'A':countA++;break;case 'e':case 'E':countE++;break;case 'i':case 'I':countI++;break;case 'o':case 'O':countO++;break;case 'u':case 'U':countU++;break;}i++;}System.out.println("A,a出现的次数为: " + countA + " 次");System.out.println("E,e出现的次数为: " + countE + " 次");System.out.println("I,i出现的次数为: " + countI + " 次");System.out.println("O,o出现的次数为: " + countO + " 次");System.out.println("U,u出现的次数为: " + countU + " 次");System.out.println("---------------------");}public void WordLength(String text) {int j = 0;StringBuffer str = new StringBuffer();while (j < text.length()) {if ((text.charAt(j) >= 'a' && text.charAt(j) <= 'z')|| (text.charAt(j) >= 'A' && text.charAt(j) <= 'Z')) { str.append(text.charAt(j));j++;} else {if (str.toString().length() > 0) {System.out.println(str.toString() + "的长度为： "+ str.toString().length());j++;str = new StringBuffer();} elsej++;}if (j == text.length() - 1) {str.append(text.charAt(j));System.out.println(str.toString() + "的长度为： "+ str.toString().length());}}}public static void main(String[] args) {Text tx = new Text();String text = "";Scanner sc = new Scanner(System.in);System.out.println("请输入文本：");text = sc.nextLine();tx.countYYZM(text);tx.WordLength(text);}}第7章、Ex_7.2import java.io.*;public class Circle {static double radius;double length;double area;public Circle(double r) {this.radius=r;}public static String readString() {BufferedReader br = new BufferedReader(new InputStreamReader(System.in), 1);String string = "";try {string = br.readLine();} catch (IOException ex) {System.out.println(ex);}return string;}public static double input() throws myException {double r;System.out.print("请输入圆的半径:\t");r=Integer.parseInt(readString());if (r < 0) {myException ex = new myException("请输入大于0的数！");throw ex;}return r;}void Length(double r) {System.out.println("圆的周长为:\t" + Math.PI * r * 2);}void Area(double r) {System.out.println("圆的面积为:\t" + Math.PI * r * r);}public static void main(String[] args){try {Circle r = new Circle(input());r.Area(radius);r.Length(radius);} catch (myException e) {e.printStackTrace();}}}class myException extends Exception {myException() {};myException(String a) {super(a);}}第8章、Ex_8.1import java.io.*;public class FileInput {File file = null;FileInput(File f) {this.file = f;};String readFile() throws IOException {FileReader fin = null;BufferedReader in;String string = "";try {fin = new FileReader(file);in = new BufferedReader(fin);String s = in.readLine();while (s != null) {string += s;s = in.readLine();}} catch (FileNotFoundException ex) {System.out.println("文件不存在！");} finally {fin.close();}return string;}char[] toArray(String s) {return s.toCharArray();}void printArray(char[] c) {for (int i = c.length - 1; i >= 0; i--) {System.out.print(c[i]);}}public static void main(String[] args) throws IOException { File file = new File("D:/text.txt");FileInput fi = new FileInput(file);String text = fi.readFile();char[] array = fi.toArray(text);fi.printArray(array);}}实验题目实验一(略)实验二(略)实验三import javax.swing.JOptionPane;public class GuessNumber{public static void main(String[] args){System.out.println("给你一个1到100的整数,请猜测这个数");int realNumber =(int)(Math.random()*100)+1; //随机生成1~100的整数 int yourGuess =0; //初始化输入的值String str =JOptionPane.showInputDialog("输入你的猜测: ");yourGuess = Integer.parseInt(str); //将输入的字符串轮换成整形//当输入的数字与随机生成的数不相等时while(yourGuess != realNumber){//输入的数大于随机生成的数if(yourGuess > realNumber){str = JOptionPane.showInputDialog("猜大了,再输入你的猜测: "); yourGuess = Integer.parseInt(str); //重置当前输入的值}//输入的数小于随机生成的数else if (yourGuess < realNumber){str = JOptionPane.showInputDialog("猜小了,再输入你的猜测: "); yourGuess = Integer.parseInt(str); //重置当前输入的值}}System.out.print("猜对了!");}}补充题:public class Main {public static void main(String[] args){float i = 0;float sum = 1; //总和int classno = 209; //学号for (i = 2;i <= classno;i++){sum += 1/i;}//输入每一项for (int j = 2; j <= classno; j++){//每十项换行if(j%10 == 0)System.out.println();System.out.print("1/" + j + " + "); }//输出总和System.out.println("和为: " + sum);}}实验四//三角形类class Triangle{double sideA, sideB, sideC, area, length; boolean boo; //能构成三角形的标记public Triangle(double a,double b,double c) {sideA=a;sideB=b;sideC=c;//如果任意两边之和不大于第三边if(((a+b)>c) &&((b+c)>a) && (a+c)>b) {boo = true; //标记为真}else{boo = false; //否则标记为假}}//三角形的周长double getLength(){//如果标记为真,即能构成三角形if(boo){length=sideA+sideB+sideC; //求周长的公式return length; //返回周长}//否则返回0else{System.out.println("不是三角形，不能计算周长"); return 0;}}//三角形边1double getsideA(){if(boo){return sideA;}else{System.out.println("边不符合要求，不能计算周长"); return 0;}}//三角形边2double getsideB(){if(boo){return sideB;}else{System.out.println("边不符合要求，不能计算周长");return 0;}}//三角形边3double getsideC(){if(boo){return sideC;}else{System.out.println("边不符合要求，不能计算周长");return 0;}}//三角形的面积public double getArea(){//如果标记为真,即能构成三角形if(boo){double p=(sideA+sideB+sideC)/2.0;area =Math.sqrt(p*(p-sideA)*(p-sideB)*(p-sideC)); //求面积公式 return area; //返回面积}//否则返回0else{System.out.println("不是三角形，不能计算面积");return 0;}}public void setABC(double a,double b,double c) {sideA = a;sideB = b;sideC = c;if(((a+b)>c)&&((a-b)<c)){boo=true;}else{boo=false;}}}//圆类class Circle{double r, area, length;public Circle(double a){r = a;}//圆的周长public double getLength(){length = Math.PI*r*2;return length;}//圆的面积public double getArea(){area = Math.PI*r*r;return area;}}//梯形类class Lader{double sideup, sidesb, sidel, sider,area, length; public Lader(double a,double b,double c,double e) {sideup = a;sidesb = b;sidel = c;sider = e;}double getLength(){length=sideup + sidesb + sidel + sider;return length;}public double getArea(){area = ((sideup + sidesb)*sidel)/2;return area;}}public class AreaAndLength{public static void main(String[] args){double length, area;double sideA,sideB,sideC;Circle circle = null;Triangle triangle;Lader lader;//调用Circle 方法返回周长并赋值给lengthcircle = new Circle(19); //修改圆的半径为19 length = circle.getLength();System.out.println("圆的周长："+ length);//调用Circle 方法返回面积并赋值给areaarea = circle.getArea();System.out.println("圆的面积："+ area);//给边值triangle = new Triangle(3,4,5);//求边sideA = triangle.getsideA();sideB = triangle.getsideB();sideC = triangle.getsideC();//输出边System.out.println("三角形的第一条边是："+ sideA);System.out.println("三角形的第二条边是："+ sideB);System.out.println("三角形的第三条边是："+ sideC);//调用Triangle 方法返回周长并赋值给lengthlength = triangle.getLength();System.out.println("三角形的周长："+ length);//调用Triangle 方法返回面积并赋值给areaarea = triangle.getArea();System.out.println("三角形的面积："+ area);//调用Lader 方法返回周长并赋值给lengthlader = new Lader(4,5,6,7);length = lader.getLength();area = lader.getArea();System.out.println("梯形的周长："+ length);//调用Lader 方法返回面积并赋值给areaSystem.out.println("梯形的面积："+ area);}}实验五//圆类class Circle{static double pi = 3.14; //静态变量//double pi = 3.14; //非静态变量不能被静态方法调用 static int objectNo = 0; //静态变量,对象的计数器int radius;//带有一个整形参数的构造函数Circle(int r){radius = r;objectNo++; //对象的计数器加1}//无参构造函数Circle(){radius = 2;objectNo++; //对象的计数器加1}//求圆的面积的方法double getArea(){return pi*radius*radius;}//静态方法(类方法)static void setPI(double p){//重置pipi = p;}void setRadius(int r){radius = r;}//静态方法static void displayNO(){//输出对象个数System.out.println("当前圆的对象个数是:\t" + objectNo);}}public class StaticTest{public static void main(String[] args){Circle cir1 = new Circle(5); //圆的对象cir1用带有一个参数的构造函数初始化System.out.println("ciir1圆周率是:\t" + cir1.pi);System.out.println("ciir1半径是:\t" + cir1.radius);System.out.println("ciir1面积是:\t" + cir1.getArea());cir1.displayNO(); //通过对象调用静态方法cir1.setRadius(10); //通过对象调用非静态方法//Circle.setRadius(10); //只有静态方法才能通过类来调用Circle cir2 = new Circle(10); //圆的对象cir2用带有一个参数的构造函数初始化cir2.setPI(3.1415); //通过对象调用静态方法System.out.println("ciir2圆周率是:\t" + cir2.pi);System.out.println("ciir2半径是:\t" + cir2.radius);System.out.println("ciir2面积是:\t" + cir2.getArea());}}实验六class ScopeTest{//类的实例变量x,mint x;static int m = 0 ; //静态变量(类变量)m,为类的所有对象共享void show(){//类的局部x变量屏蔽掉类的实例xint x = 8,y;//类的局部变量xfor(y = 0; y < 2; y++) //循环两次{//z是局部变量,属方法域中的变量,因此作用范围只在此for()语句中.//int z = 5;//局部变量不能重名int z = 5;System.out.println("z = " + z);z = 10; //重置z的值为10System.out.println("z = " + z);System.out.println("方法域中的X = " + z + "在块内显示");}//去掉注释后错误是z中此方法中未声明,因为z的作用范围只在for()循环语句块中.//z = 20;System.out.println("方法域中的X = " + x + " 在块外显示");System.out.println("类域中的x = " + this.x + " 在块外显示");System.out.println("类域中的m = " + this.m + " 在块外显示");}void setx(int x){this.x = x; //赋值实例变量的值为2}//静态方法(类方法)只能访问静态变量(类变量)static void setm(int m)//void setm(int m) //此时是非静态方法,this指代的是对象.{//在静态方法中通过类名调用静态变量ScopeTest.m = m; //赋值静态变量m的值为3// this.m = m; //在静态方法中不能有this,因为静态方法属于整个类,而不是某个对象}public static void main(String[] args){ScopeTest application = new ScopeTest(); //声明ScopeTest类的对象applicationapplication.setx(2); //调用方法setx(int x)application.setm(3); //调用方法setm(int x)application.show(); //调用方法show()}}实验七(非重点略)实验八(非重点略)。