Java语言程序设计(第2版)第1-6章 课后习题答案解析

Java语言程序设计第2版(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。

//习题2.2import java.util.*;class MyDate{private int year;private int month;private int day;public MyDate(int y,int m,int d){//构造函数，构造方法year=y;month=m;day=d;}//end public MyDate(int y,int m,int d)public int getYear(){//返回年return year;}//end getYear()public int getMonth(){//返回月return month;}//end getMonth()public int getDay(){//返回日return day;}//end getDay()}//end class MyDateclass Employee{private String name;private double salary;private MyDate hireDay;public Employee(String n,double s,MyDate d){name=n;salary=s;hireDay=d;}//end public Employee(String n,double s,MyDate d)public void print(){System.out.println("名字:"+name+"\n工资:"+salary+"\n雇佣年份:"+hireYear()+"\n");}//end print()public void raiseSalary(double byPercent){salary*=1+byPercent/100;}//endpublic int hireYear(){return hireDay.getYear();}}//end class Employeepublic class MyTestClass {public static void main(String[] args) {Employee[]staff=new Employee[3];staff[0]=new Employee("Harry Hacker",35000,new MyDate(1989,10,1));- 2 - staff[1]=new Employee("Carl Carcker",75000,new MyDate(1987,12,15)); staff[2]=new Employee("Tony T ester",38000,new MyDate(1990,3,12)); int integerValue;System.out.println("The information of employee are:");for(integerValue=0;integerValue<=2;integerValue++){staff[integerValue].raiseSalary(5);}//end for()for(integerValue=0;integerValue<=2;integerValue++){staff[integerValue].print();}//end for()}//end main() }//end class MyTestClass//习题2.4import java.util.*;public class DataType {public static void main(String[] args) {boolean flag;char yesChar;byte finByte;int intValue;long longValue;short shortValue;float floatValue;double doubleValue;flag=true;yesChar='y';finByte=30;intValue=-7000;longValue=200l;shortValue=20000;floatValue=9.997E-5f;doubleValue=floatValue*floatValue;System.out.println("the values are:");System.out.println("布尔类型变量flag="+flag);System.out.println("字符型变量yesChar="+yesChar);System.out.println("字节型变量finByte="+finByte);System.out.println("整型变量intValue="+intValue);System.out.println("长整型变量longValue="+longValue);System.out.println("短整型变量shortValue="+shortValue);System.out.println("浮点型变量floatValue="+floatValue);System.out.println("双精度浮点型变量doubleValue="+doubleValue);}//end main()}//习题2.9import java.util.*;class PubTest1{private int ivar1;private float fvar1,fvar2;public PubTest1(){fvar2=0.0f;}public float sum_f_I(){fvar2=fvar1+ivar1;return fvar2;}public void print(){System.out.println("fvar2="+fvar2);}public void setIvar1(int ivalue){ivar1=ivalue;}public void setFvar1(float ivalue){fvar1=ivalue;}}public class PubMainTest {public static void main(String[] args) {PubTest1 pubt1=new PubTest1();pubt1.setIvar1(10);pubt1.setFvar1(100.02f);pubt1.sum_f_I();pubt1.print();}}//习题2.10import java.util.*;class Date {private int year;private int month;private int day;public Date(int day, int month, int year) { //构造函数，构造方法this.year = year;this.month = month;this.day = day;} //end public MyDate(int y,int m,int d)- 4 -public int getYear() { //返回年return year;} //end getYear()public int getMonth() { //返回月return month;} //end getMonth()public int getDay() { //返回日return day;} //end getDay()} //end class Datepublic class Teacher {String name;//教师名字boolean sex;//性别，true 表示男性Date birth;//出生日期String salaryID;//工资号String depart;//教师所在系所String posit;//教师职称String getName() {return name;}void setName(String name) { = name;}boolean getSex() {return sex;}void setSex(boolean sex) {this.sex = sex;}Date getBirth() {return birth;}void setBirth(Date birth) {this.birth = birth;}String getSalaryID() {return salaryID;}void setSalaryID(String salaryID) {this.salaryID = salaryID;}String getDepart() {return depart;}void setDepart(String depart) {this.depart = depart;}String getPosit() {return posit;}void setPosit(String posit) {this.posit = posit;}public Teacher(){System.out.println("父类无参数的构造方法！！！！！！！");}//如果这里不加上这个无参数的构造方法将会出错！！！！public Teacher(String name,boolean sex,Date birth,String salaryid,String depart,String posit){ =name;this.sex=sex;this.birth=birth;this.salaryID=salaryid;this.depart=depart;this.posit=posit;}//end Teacher()public void print(){System.out.print("the teacher'name:");System.out.println(this.getName());System.out.print("the teacher'sex:");if(this.getSex()==false){System.out.println("女");}else{System.out.println("男");}System.out.print("the teacher'birth:");System.out.println(this.getBirth().getYear()+"-"+this.getBirth().getMonth()+"-"+this.getBirth().getDay()); System.out.print("the teacher'salaryid:");System.out.println(this.getSalaryID());System.out.print("the teacher'posit:");System.out.println(this.getPosit());System.out.print("the teacher'depart:");System.out.println(this.getDepart());}//end print()public static void main(String[] args) {Date dt1=new Date(11,23,1989);Date dt2=new Date(2,6,1975);- 6 -Date dt3=new Date(11,8,1964);Date dt4=new Date(10,4,1975);Date dt5=new Date(8,9,1969);//创建各系教师实例，用来测试Teacher t1=new Teacher("王莹",false,dt1,"123","经济学","prefessor");ResearchTeacher rt=new ResearchTeacher("杨zi 青",true,dt2,"421","软件工程", "associate prefessor","software"); LabTeacher lat=new LabTeacher("王夏瑾",false,dt3,"163","外语","pinstrucor","speech lab");LibTeacher lit=new LibTeacher("马二孩",true,dt4,"521","大学物理","prefessor","physicalLib");AdminTeacher at=new AdminTeacher("王xi",false,dt5,"663","环境","prefessor","dean");/////////分别调用各自的输出方法，输出相应信息//////////////////////////// System.out.println("-------------------------------");t1.print();//普通教师信息System.out.println("-------------------------------");rt.print();//研究系列教师信息System.out.println("-------------------------------");lat.print();//普通教师信息System.out.println("-------------------------------");lit.print();//实验系列教师信息System.out.println("-------------------------------");at.print();//行政系列教师信息System.out.println("-------------------------------");}//end main()}//end public class Teacherclass ResearchT eacher extends Teacher{private String resField;public ResearchT eacher(String name, boolean sex, Date birth, String salaryid, String depart, String posit, String resField) { = name;this.sex = sex;this.birth = birth;this.salaryID = salaryid;this.depart = depart;this.posit = posit;this.resField = resField;} //end public ResearchTeacher(){}String getResField(){return resField;}void setResField(String resField){this.resField=resField;}public void print() {System.out.print("research teacher info is:");System.out.print("the teacher'name:");System.out.println(this.getName());System.out.print("the teacher'sex:");if (this.getSex() == false) {System.out.println("女");}else {System.out.println("男");}System.out.print("the teacher'birth:");System.out.println(this.getBirth().getYear() + "-" +this.getBirth().getMonth() + "-" +this.getBirth().getDay());System.out.print("the teacher'salaryid:");System.out.println(this.getSalaryID());System.out.print("the teacher'posit:");System.out.println(this.getPosit());System.out.print("the teacher'depart:");System.out.println(this.getDepart());System.out.print("the teacher'resField:");System.out.println(this.getResField());} //end print()}//end class ResearchTeacherclass LabTeacher extends T eacher{private String labName;public LabTeacher(String name, boolean sex, Date birth,String salaryid, String depart,String posit, String labName) { = name;this.sex = sex;this.birth = birth;this.salaryID = salaryid;this.depart = depart;this.posit = posit;bName = labName;} //end public ResearchTeacher(){}String getLabName(){return labName;}void setLabName(String labName){- 8 -bName=labName;}public void print() {System.out.print("lab teacher info is:");System.out.print("the teacher'name:");System.out.println(this.getName());System.out.print("the teacher'sex:");if (this.getSex() == false) {System.out.println("女");}else {System.out.println("男");}System.out.print("the teacher'birth:");System.out.println(this.getBirth().getYear() + "-" +this.getBirth().getMonth() + "-" +this.getBirth().getDay());System.out.print("the teacher'salaryid:");System.out.println(this.getSalaryID());System.out.print("the teacher'posit:");System.out.println(this.getPosit());System.out.print("the teacher'depart:");System.out.println(this.getDepart());System.out.print("the teacher'labName:");System.out.println(bName);} //end print()}//end class LabTeacherclass LibTeacher extends Teacher{private String libName;public LibTeacher(String name,boolean sex,Date birth,String salaryid,String depart,String posit,String libName){ = name;this.sex = sex;this.birth = birth;this.salaryID = salaryid;this.depart = depart;this.posit = posit;this.libName=libName;}//end public ResearchT eacher(){}String getLibName(){return libName;}void setLibName(String libName){this.libName=libName;}public void print() {System.out.print("lib teacher info is:");System.out.print("the teacher'name:");System.out.println(this.getName());System.out.print("the teacher'sex:");if (this.getSex() == false) {System.out.println("女");}else {System.out.println("男");}System.out.print("the teacher'birth:");System.out.println(this.getBirth().getYear() + "-" +this.getBirth().getMonth() + "-" +this.getBirth().getDay());System.out.print("the teacher'salaryid:");System.out.println(this.getSalaryID());System.out.print("the teacher'posit:");System.out.println(this.getPosit());System.out.print("the teacher'depart:");System.out.println(this.getDepart());System.out.print("the teacher'libName:");System.out.println(this.libName);} //end print()}//end class LibTeacherclass AdminTeacher extends Teacher{private String managePos;public AdminTeacher(String name,boolean sex,Date birth,String salaryid,String depart,String posit,String managePos){ = name;this.sex = sex;this.birth = birth;this.salaryID = salaryid;this.depart = depart;this.posit = posit;this.managePos=managePos;- 10 -}//end public ResearchT eacher(){}String getManagePos(){return managePos;}void setManagePos(String managePos){this.managePos=managePos;}public void print() {System.out.print("adminteacher info is:");System.out.print("the teacher'name:");System.out.println(this.getName());System.out.print("the teacher'sex:");if (this.getSex() == false) {System.out.println("女");}else {System.out.println("男");}System.out.print("the teacher'birth:");System.out.println(this.getBirth().getYear() + "-" +this.getBirth().getMonth() + "-" +this.getBirth().getDay());System.out.print("the teacher'salaryid:");System.out.println(this.getSalaryID());System.out.print("the teacher'posit:");System.out.println(this.getPosit());System.out.print("the teacher'depart:");System.out.println(this.getDepart());System.out.print("the teacher'managePos:");System.out.println(this.managePos);} //end print() }//end class AdminTeacher习题2.11public class Course {private String courseID;private String courseName;private String courseType;private int classHour;private float credit;public Course(String courseID, String courseName, String courseType, int classHour, float credit) {this.courseID=courseID;this.courseName=courseName; this.courseType=courseType; this.classHour=classHour; this.credit=credit;}//end public Course(){}String getID() {return courseID;}void setID(String id) {this.courseID = id;}String getName() {return courseName;}void setName(String name) { this.courseName = name;}String getType() {return courseType;}void setType(String type) { this.courseType = type;}int getClassHour() {return classHour;}void setClassHour(int hour) { this.classHour = hour;}float getCredit() {return classHour;}void setCredit(float credit) { this.credit= credit;}- 12 -public void print(){System.out.println("the basic info of this course as followed:"); System.out.println("courseID="+this.getID());System.out.println("courseName="+this.getName());System.out.println("courseType="+this.getType());System.out.println("classHour="+this.getClassHour());System.out.println("credit="+this.getCredit());}public static void main(String[] args) {Course cs=new Course("d12","java 程序设计(第二版)","cs",64,3.0f); System.out.println("----------------------------------");cs.print();System.out.println("修改课程学分为4.0f");cs.setCredit(4);cs.print();} }//习题2.12public class MyGraphic {String lineColor;String fillColor;MyGraphic(String lc,String fc){this.lineColor=lc;this.fillColor=fc;}void print(){System.out.println("line color is "+this.lineColor+"\t fill color is "+this.fillColor);}public static void main(String[] args) {float rd=(float)4.5;MyCircle mc=new MyCircle(rd,"black","white");MyRectangle mr=new MyRectangle(4,6,"red","blue");System.out.println("Circle info ");mc.print();System.out.println("circumference is " + mc.calCircum());System.out.println("square is " + mc.calSquare());System.out.println("rectangle info: ");mr.print();System.out.println("circumference is " + mr.calCircum());System.out.println("square is " + mr.calSquare()); }//end main(){}}//end public class MyGraphicclass MyRectangle extends MyGraphic{float rLong;float rWidth;MyRectangle (float rl,float rw,String lc,String fc){super(lc,fc);this.rLong=rl;this.rWidth=rw;}//end MyRectangle (){}float calCircum(){return ((float)((this.rLong+this.rWidth)*2));}float calSquare(){return ((float)(this.rLong*this.rWidth));}}//end class MyRectangleclass MyCircle extends MyGraphic{float radius;MyCircle (float rd,String lc,String fc){super(lc,fc);this.radius=rd;}//end MyRectangle (){}float calCircum(){return (float)((this.radius*3.12*2));}float calSquare(){return ((float)(this.radius*this.radius*3.14));}}//end class MyCircle//习题2.13public class Vehicle {String brand;String color;int price;int number;- 14 -public Vehicle(String b, String c) {this.brand = b;this.color = c;}public Vehicle(String b, String c, int p, int n) {this(b, c);this.price = p;this.number = n;}void print() {System.out.println("\n-------------------------");System.out.println("the vehicle info as followed :");System.out.println("brand=" + this.brand + "\t");System.out.println("color=" + this.color + "\t");System.out.println("price=" + this.price + "\t");System.out.println("number=" + this.number + "\t");} //end void print()public static void main(String[] args) {Vehicle c1=new Vehicle("vehicle1","white");Vehicle c2=new Vehicle("vehicle2","white",300,1);Car cr=new Car("car1","red",300,4,400);Truck tk2=new Truck("truck1","black",300,400);c1.print();c2.print();cr.print();tk2.print();} //end main()} //end public class Vehicleclass Car extends Vehicle{int speed;Car(String b, String c, int p, int n,int s){super(b,c,p,n);this.speed=s;}void print(){super.print();System.out.print("speed="+this.speed);}}//end class Carclass Truck extends Vehicle{int weight;Truck(String b, String c, int s,int w){super(b,c);this.speed=s;this.weight=w;}void print(){super.print();System.out.print("speed="+this.speed);System.out.print("weight="+this.weight); }}//end class Truck//习题3.3public class Test {public static void main(String[] args) {int b1=1;int b2=1;System.out.println("b1=" + b1);System.out.println("b2=" + b2);b1<<=31;b2<<=31;System.out.println("b1=" + b1);System.out.println("b2=" + b2);b1 >>= 31;System.out.println("b1=" + b1);b1 >>= 1;System.out.println("b1=" + b1);b2 >>>= 31;System.out.println("b2=" + b2);b2 >>>= 1;System.out.println("b2=" + b2);}}//习题3.4public class Factorial {private int result,initVal;public static int Factorial(int n){if(n==0){- 16 -}return n*Factorial(n-1);}public void print(){System.out.println(initVal+"!="+result);}public void setInitVal(int n){initVal=n;}public static void main(String[] args) {Factorial ff=new Factorial();for(int i=0;i<=4;i++){ff.setInitVal(2*(i+1));ff.result=Factorial(ff.initVal);ff.print();}//end for()}//end main()}//end public class Factorialpublic class Factorial2 {private int result,initVal;public void print(){System.out.println(initVal+"!="+result);}public void setInitVal(int n){initVal=n;}public static void main(String[] args) {Factorial2 ff=new Factorial2();for(int i=0;i<=4;i++){ff.setInitVal(2*(i+1));ff.result=1;for(int j=2;j<=ff.initVal;j++){ff.result*=j;}ff.print();}//end for()}//end main() }//习题3.5public class MathRandomTest {public static void main(String[] args) {int count=0,MAXof100,MINof100;int num,i;MAXof100=(int)(100*Math.random());MINof100=(int)(100*Math.random());System.out.print(MAXof100+" ");System.out.print(MINof100+" ");if(MAXof100>50)count++;if(MINof100>50)count++;if( MAXof100<MINof100){num=MINof100;MINof100=MAXof100;MAXof100=num;}//end if()for(i=0;i<98;i++){num=(int)(100*Math.random());System.out.print(num+((i+2)%10==9?"\n":" "));if(num>MAXof100){MAXof100=num;}else if(num<MINof100){MINof100=num;}if(num>50){count++;}}//end for()System.out.println("the max of 100 random integers is "+MAXof100);System.out.println("the min of 100 random integers is "+MINof100);System.out.println("the number of random more than50 is "+count); }//end main()}//end public class MathRandomTest//习题3.7public class PrintAst {public void printAstar() {System.out.print("*");}public void printSpace() {System.out.print(" ");}- 18 -public static void main(String[] args) {PrintAst pa = new PrintAst();int initNum = 13;for (int i = 1; i <= initNum / 2 + 1; i++) {for (int n = 1; n <= i; n++) {pa.printSpace();pa.printSpace();}for (int m = 1; m <= initNum - 2 * i + 2; m++) {pa.printSpace();pa.printAstar();}System.out.println();} //end forif (initNum % 2 == 0) {for (int i = 1; i <= initNum / 2; i++) {pa.printSpace();pa.printSpace();}pa.printSpace();pa.printAstar();pa.printSpace();pa.printAstar();System.out.println();}for (int i = initNum / 2 + 2; i <= initNum; i++) {for (int n = 1; n <= initNum - i + 1; n++) {pa.printSpace();pa.printSpace();}for (int m = 1; m <= 2 * i - initNum; m++) {pa.printSpace();pa.printAstar();}System.out.println();} //end forSystem.out.println();} //end main()} //end public class PrintAst//习题3.8public class PrintTriag {public void printAstar() {System.out.print("*");}public static void main(String[] args) {int initLine = 10;int initNum = 10;PrintTriag pt = new PrintTriag();for (int i = 0; i < initLine; i++) {for (int j = 0; j < initNum - i; j++) {pt.printAstar();}System.out.println();}}//end main()}//end public class PrintTriag习题3.9import java.util.*;public class MultipleT able {public void printFormula(int i,int j,int res){ System.out.print(i+"*"+j+"="+res+" "); }public static void main(String[] args) {MultipleT able mt=new MultipleT able();int initNum=9;int res=0;for(int i=1;i<=initNum;i++){for(int j=1;j<=i;j++){res=i*j;mt.printFormula(i,j,res);}System.out.println();}//end for}//end main()- 20 - }//end public class MultipleT able习题3,10import java.io.*;public class HuiWen {boolean isHuiWen(char str[], int n) {int net = 0;int i, j;for (i = 0, j = n - 1; i < n / 2; i++, j--) {if (str[i] == str[j]) {net++;} //end if} //end forif (net == (int) (n / 2)) {return true;} //end ifelse {return false;}} //end boolean isHuiWen(char str[], int n)public static void main(String[] args) {HuiWen hw1 = new HuiWen();String pm = "";try {InputStreamReader reader = new InputStreamReader(System.in); BufferedReader input = new BufferedReader(reader);System.out.print("give your test string:\n");pm = input.readLine();System.out.println(pm);} //end trycatch (IOException e) {System.out.print(e);} //end catchboolean bw = hw1.isHuiWen(pm.toCharArray(), pm.length()); if (bw == true) {System.out.println("是回文");}else {System.out.println("不是回文");}} //end main()} //end public class HuiWenimport java.io.*;public class HuiWen2 {String reverse(String w1){String w2;char[]str1=w1.toCharArray();int len=w1.length();char[]str2=new char[len];for(int i=0;i<len;i++){str2[i]=str1[len-1-i];}w2=new String(str2);return w2;}public static void main(String[] args) {HuiWen2 hw1 = new HuiWen2();String pm = "";try {InputStreamReader reader = new InputStreamReader(System.in);BufferedReader input = new BufferedReader(reader);System.out.print("give your test string:\n");pm = input.readLine();} //end trycatch (IOException e) {System.out.print(e);} //end catchString w2=hw1.reverse(pm);if(pareTo(pm)==0){System.out.println("是回文");}else {System.out.println("不是回文");}}}//习题3.11import java.io.*;public class PrimeNumber {- 22 -private int pm;public void setPm(int pm){this.pm=pm;}public boolean isPrime(){boolean bl=true;int i=2;for(i=2;i<=Math.sqrt(pm);){if(pm%i==0){bl=false;break;}else{i++;}}//end forreturn bl;}//end public boolean isPrime()public static void main(String[] args) {PrimeNumber prim=new PrimeNumber();int testNum=0;try{InputStreamReader reader = new InputStreamReader(System.in);BufferedReader input = new BufferedReader(reader);System.out.print("give your test number:\n");testNum=Integer.parseInt(input.readLine());}//end trycatch(IOException e){System.out.println(e);}//end catchprim.setPm(testNum);boolean bl=prim.isPrime();if(bl==true){System.out.println(testNum+"是质数");}else {System.out.println(testNum+"不是质数");}}//end main }//end public class PrimeNumber习题3.12import java.io.*;public class Tempconverter {double celsius(double y){return ((y-32)/9*5);}public static void main(String[] args) {Tempconverter tc=new Tempconverter ();double tmp=0;try{InputStreamReader reader = new InputStreamReader(System.in);BufferedReader input = new BufferedReader(reader);System.out.print("give your fahrenheit number:\n");tmp=Double.parseDouble(input.readLine());}//end trycatch(NumberFormatException e){System.out.println(e);}//end catchcatch(IOException e){System.out.println(e);}//end catchSystem.out.println("the celsius of temperature is "+tc.celsius(tmp));}//end main()}//end public class Tempconverter习题3.13import java.io.*;public class Trigsquare {double x, y, z;Trigsquare(double x, double y, double z) {this.x = x;this.y = y;this.z = z;}boolean isTriangle() {boolean bl = false;if (this.x > 0 && this.y > 0 && this.z > 0) {if ( (this.x + this.y) > this.z && (this.x + this.z) > this.y && (this.z + this.y) > this.x) {bl = true;} //ebd ifelse {bl = false;} //end else} //end if(this.x>0&&this.y>0&&this.z>0)return bl;} //end boolean isTriangle()double getArea() {double s = (this.x + this.y + this.z) / 2.0;return (Math.sqrt(s * (s - this.x) * (s - this.y) * (s - this.z)));} //end double getArea()public static void main(String[] args) {double s[] = new double[3];try {InputStreamReader reader = new InputStreamReader(System.in);BufferedReader input = new BufferedReader(reader);System.out.print("输入三角形的三边的长度:\n");for (int i = 0; i <= 2; i++) { //输入三个数s[i] = Double.parseDouble(input.readLine());} //end for} //end trycatch (NumberFormatException e) {System.out.println("format error!!!");} //end catch- 24 - catch (IOException e) {System.out.print(e);} //end catchTrigsquare ts = new Trigsquare(s[0], s[1], s[2]);if (ts.isTriangle() == true) {System.out.println("三角形的面积是" + ts.getArea());} //end ifelse {System.out.println("输入的三边不能组成三角形！！");} //end else} //end main()} //end public class Trigsquare//习题3.14import java.util.*;import java.io.*;import java.util.Date;import java.text.*;import java.text.DateFormat;import java.text.SimpleDateFormat;import java.util.GregorianCalendar.*;。

习题一‎1．‎简述面向‎对象软件开‎发方法的重‎要意义。

‎‎【答】：‎面向对‎象的软件开‎发方法按问‎题论域来设‎计模块，以‎对象代表问‎题解的中心‎环节，力求‎符合人们‎日常的思维‎习惯，采用‎―对象+消‎息‖的程序‎设计模式，‎降低或分解‎问题的难度‎和复杂性‎，从而以较‎小的代价和‎较高的收益‎获得较满意‎的效果，满‎足软件工程‎发展需要。

‎‎2．解释‎下面几个概‎念：‎1）对象‎2）实例‎3）类 4‎）消息 5‎）封装 6‎）继承 7‎）多态‎【答】：‎1）‎对象：就‎是现实世界‎中某个具体‎的物理实体‎在计算机中‎的映射和体‎现,是由属‎性和操作‎所构成的一‎个封闭整体‎。

‎2）实例‎：是对象在‎计算机内存‎中的映像。

‎3‎）类：是‎描述对象的‎―基本原型‎‖，是描述‎性的类别或‎模板，即对‎一组对象的‎抽象。

它‎定义一组对‎象所能拥有‎的共同特征‎，用以说明‎该组对象的‎能力与性质‎。

‎4）消息‎：消息是对‎象之间进行‎通信的一种‎数据结构。

‎5‎）封装：‎封装性是保‎证软件部件‎具有优良的‎模块性的基‎础。

面向对‎象的类是封‎装良好的‎模块，类定‎义将其说明‎（用户可见‎的外部接口‎）与实现（‎用户不可见‎的内部实现‎）显式地‎分开，其内‎部实现按其‎具体定义的‎作用域提供‎保护。

‎6）‎继承：继承‎性是子类自‎动共享父类‎数据结构和‎方法的机制‎，这是类之‎间的一种关‎系。

‎7）多‎态：多态性‎是指一个名‎字具有多种‎语义，即指‎同一消息为‎不同对象所‎接受时，可‎以导致不‎同的操作。

‎‎3．‎对象―汽车‎‖与对象―‎小汽车‖是‎什么关系，‎对象―汽车‎‖与―轮胎‎‖又是什么‎关系？‎‎【答】：‎对象‎―汽车‖与‎对象―小汽‎车‖具有继‎承关系，即‎对象―小汽‎车‖继承了‎对象―汽车‎‖。

―轮‎胎‖是对象‎―汽车‖的‎一个属性，‎所以对象―‎汽车‖包含‎―轮胎‖，‎二者是包含‎关系。

第一章：P561、列出在你过去学习工作中用过与计算机图形学有关的程序c语言：#include&lt;graphics.h&gt;main(){intgraphdriver=VGA,graphmode=VGAHI;initgraph(&graphdriver,&graphmode,””);setbkcolor(BLUE);setcolor(WHITE);setfillstyle(1,LIGHTRED);bar3d(100,200,400,350,100,1);floodfill(450,300,WHITE);floodfill(250,450,WHITE);setcolor(LIGHTGREEN);rectangle(450,400,500,450);floodfill(470,420,LIGHTGREEN);getch();closegraph();}JAVA语言：例1、画点Importjava.io.*;Classpoint{intax;intay;intbx;intby;publicpoint(intax,intay,intbx,intby){floatk;//计算斜率floatb;k=(by-ay)/(bx-ax);b=ay-ax*k;system.out.println(“直线的方程为：y=”+k+”x”+”+”+b);}}例2、画矩形classDrawPanelextendsJpanel{publicvoidpaint(Graphicsg){super.paint(g);Graphics2Dg2=(Graphics2D);Doubleleftx=200;Doubletopy=200;Doublewidth=300;Doubleheight=250;Rectangle2Drect=newRectangle2D.double(leftx,topy,width,height);G2.draw(rect);}}2、列出你所用过的窗口系统中与观感有关的元素的功能，如图标、滚动棒、菜单等使用滚动条当文档、网页或图片超出窗口大小时，会出现滚动条，可用于查看当前处于视图之外的信息。

java程序设计第二版课后答案Java程序设计第二版课后答案涵盖了多个章节，每个章节都包含了不同的编程概念和练习题。

以下是一些常见章节的课后答案概要，以供参考：第1章：Java简介- 1.1 Java的起源和特点- 1.2 Java平台的组成- 1.3 Java开发环境的搭建第2章：基本语法- 2.1 数据类型- 2.2 变量声明- 2.3 运算符- 2.4 控制语句（if, switch, loop）第3章：控制流程- 3.1 条件语句（if-else, switch-case）- 3.2 循环语句（for, while, do-while）- 3.3 跳转语句（break, continue, return）第4章：数据结构- 4.1 数组的定义和使用- 4.2 字符串的处理- 4.3 集合框架简介第5章：面向对象编程- 5.1 类和对象- 5.2 构造方法- 5.3 继承- 5.4 封装和多态第6章：异常处理- 6.1 异常的概念- 6.2 异常的分类- 6.3 异常的处理方式（try-catch-finally）第7章：输入输出- 7.1 标准输入输出- 7.2 文件输入输出- 7.3 序列化第8章：Java集合框架- 8.1 集合的基本概念- 8.2 List接口及其实现- 8.3 Set接口及其实现- 8.4 Map接口及其实现第9章：泛型- 9.1 泛型的概念- 9.2 泛型的使用- 9.3 泛型的限制第10章：多线程- 10.1 线程的概念- 10.2 创建和启动线程- 10.3 线程的同步第11章：网络编程- 11.1 网络编程基础- 11.2 Socket编程- 11.3 URL和URLConnection第12章：图形用户界面- 12.1 AWT和Swing- 12.2 事件处理- 12.3 布局管理器第13章：Java数据库连接- 13.1 JDBC基础- 13.2 数据库连接和操作- 13.3 SQL语句的使用第14章：Java Web应用- 14.1 Servlet基础- 14.2 JSP技术- 14.3 MVC架构模式每个章节的课后答案通常包括理论问题和编程练习题的解答。

java语言程序设计第二版习题答案Java语言程序设计第二版习题答案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。

无论是初学者还是有经验的开发人员，都可以通过学习Java语言来提升自己的编程能力。

为了帮助读者更好地掌握Java语言的知识，本文将提供《Java语言程序设计第二版》中一些习题的答案，并对其中一些重要的概念进行解释和讨论。

第一章：计算机、程序和Java1.1 问题：编写一个Java程序，输出“Hello, World!”。

答案：```javapublic class HelloWorld {public static void main(String[] args) {System.out.println("Hello, World!");}}```1.2 问题：Java应用程序的执行过程是怎样的？答案：Java应用程序的执行过程可以分为三个阶段：编辑、编译和运行。

首先，我们使用文本编辑器编写Java源代码文件，文件的扩展名为.java。

然后，使用Java编译器将源代码文件编译成字节码文件，文件的扩展名为.class。

最后，使用Java虚拟机(JVM)加载字节码文件并执行程序。

第二章：基本程序设计2.1 问题：编写一个Java程序，计算两个整数的和。

答案：```javaimport java.util.Scanner;public class Sum {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter the first number: ");int num1 = input.nextInt();System.out.print("Enter the second number: ");int num2 = input.nextInt();int sum = num1 + num2;System.out.println("The sum is " + sum);}}```2.2 问题：什么是变量？如何在Java中声明和使用变量？答案：变量是用于存储数据的内存位置。

第1章Java语言概述选择题1-1 在下列概念中，Java语言只保留了（B）A. 运算符重载B. 方法重载C. 指针D. 结构和联合1-2 下列关于Java语言特性的描述中，错误的是（D）A. 支持多线程操作B. Java程序与平台无关C. Java和程序可以直接访问Internet上的对象D. 支持单继承和多继承1-3 下列关于Java Application程序在结构上的特点的中，错误的是（C）A. Java程序是由一个或多个类组成的B. 组成Java程序的若干个类可以放在一个文件中，也可以放在多个文件中C. Java程序的文件名要与某个类名相同D. 组成Java程序的多个类中，有且仅有一个主类1-4 Java程序经过编译后生成的文件的后缀是（C）A. .objB. .exeC. .classD. .java1-5 下列关于运行字节码文件的命令行参数的描述中，正确的是（A）A. 第一个命令行参数（紧跟命令字的参数）被存放在args[0]中B. 第一个命令行参数被存放在args[1]中C. 命令行的命令字被存放在args[0]中D.数组args[]的大小与命令行参数的个数无关判断题1-1JavaC++的语言之前问世的。

（错）1-2Java语言具有较好的安全性和可移植性及与平台无关等特性。

（对）1-3Java语言中取消了联合的概念，保留了结构概念。

（错）1-4Java语言中数据类型占内在字节数与平台无关。

（对）1-5Java语言中可用下标和指针两种方式表示数组元素。

（错）1-6Java语言的源程序不是编译型的，而是编译解释型的。

（对）1-7操作系统中进程和线程两个概念是没有区别的。

（错）1-8Java语言既是面向对象的又是面向网络的高级语言。

（对）1-9Java程序分为两大类：一类是Application程序，另一类是Applet程序。

前者又称Java应用程序，后者又称为Java小应用程序。

（对）1-10Java Application程序是由多个文件组成的，其中可以有也可以没有主文件。