Java语言程序设计(基础篇)原书第十一版梁勇第9章课后题答案

1、9.1 设计一个名为 Rectangle 的类表示矩形public class Testpublic static void main(String args) Rectangle rectangle1=new Rectangle(4,40);System.out.println(矩形的宽是 +rectangle1.width+, 高是 +rectangle1.height+,面积是+rectangle1.getArea()+，周长是 +rectangle1.getPerimeter();Rectangle rectangle2=new Rectangle(3.5,35.9);System.o

2、ut.print( 矩形的宽是 +rectangle2.width+, 高是 +rectangle2.height+, 面积是+rectangle2.getArea()+，周长是 +rectangle2.getPerimeter();class Rectangledouble width=1;double height=1;Rectangle()Rectangle(double newWidth,double newHeight)width=newWidth;height=newHeight;double getArea()return width*height;double getPerim

3、eter()return (width+height)*2;9.3 使用 Date 类public class Test public static void main(String args) Date date = new Date();long l=10000;for(int i = 1; i 9; i+) date.setTime(l);printDate(l, date);l*=10;public static void printDate(long l, Date date) System.out.println(l + : + date.toString();9.4 使用 Ran

4、dom 类public class Test public static void main(String args) Random random=new Random(1000);for (int i=1;i51;i+)System.out.print(random.nextInt(100)+t);if (i%10=0)System.out.println();9.6 秒表public class Test public static void main(String args) StopWatchstopWatch=new StopWatch();stopWatch.start();int

5、 a = new int100000;for (int i=0;i100000;i+)ai=(int)(Math.random()*200);count(a);stopWatch.stop();System.out.print(测试所用时间为： +stopWatch.getElapsedTime()+ms);public static void count(int a)int max ;int tmp ;for(int i=0;ia.length;i+)max = i;for(int j=i+1;ja.length;j+)if(amaxaj)max = j;if(i!=max)tmp = ai

6、;ai = amax;amax = tmp;class StopWatch private long startTime;private long endTime;StopWatch()startTime = System.currentTimeMillis();public void start()startTime = System.currentTimeMillis();public void stop()endTime = System.currentTimeMillis();public long getElapsedTime()return endTime - startTime;

7、9.7 Accont 类public class DemoA public static void main(String args) Account account=new Account();Scanner in=new Scanner(System.in);System.out.println( 创建用户，依次输入 id、balance、annualInterestRate：);int id=in.nextInt();double balance=in.nextDouble();double annualInterestRate=in.nextDouble();account.Chuan

8、gJian(id,balance,annualInterestRate);System.out.print(请输入取款额： ); intmoney=in.nextInt();account.withDraw(money);System.out.print(请输入存款额： );money=in.nextInt();account.deposit(money);account.Print();class Accountprivate int id;private double balance;private double annualInterestRate;private Date dateCr

9、eated;public void Print()System.out.println( 余额为： +balance);System.out.println( 月利息为： +getMonthlyInterset();System.out.print(开户日期为： );getDate();public void ChuangJian()id=0;balance=0;annualInterestRate=0;public void ChuangJian(int id,double balance,doubleannualInterestRate) this.id=id;this.balance=b

10、alance;this.annualInterestRate=annualInterestRate;this.dateCreated = new Date();public void Look()System.out.println(id ：+id);System.out.println(balance：+balance);System.out.println(annualInterestRate：+annualInterestRate);public void Change(int id)System.out.println( 请输入更改后的 id、 balance、annualIntere

11、stRate);Scanner in=new Scanner(System.in);this.id=in.nextInt();this.balance=in.nextDouble();this.annualInterestRate=in.nextDouble();public Date getDate()System.out.println(dateCreated);return dateCreated;public double getMonthlyInterestRate()return annualInterestRate/12;public double getMonthlyInter

12、set()return getMonthlyInterestRate()*balance;public void withDraw(int moneyOut)balance-=moneyOut;public void deposit(int moneyIn)balance+=moneyIn;9.8 Fan 类public class DemoB public static void main(String args) Fan fan1=new Fan();fan1.setSpeed(3);fan1.setRadius(10);fan1.setColor(yellow);fan1.setOn(t

13、rue);System.out.println(fab1:+fan1.toString();Fan fan2=new Fan();fan2.setSpeed(2);fan2.setRadius(5);fan2.setColor(blue);fan2.setOn(false);System.out.println(fab2:+fan2.toString();class Fanint SLOW=1;int MEDIUM=2;int FAST=3;private int speed=SLOW;private boolean on=false;private double radius=5;Strin

14、g color=blue;public Fan()public int getSpeed() return speed;public void setSpeed(int speed) this.speed = speed;public boolean isOn() return on;public void setOn(boolean on) this.on = on;public double getRadius() return radius;public void setRadius(double radius) this.radius = radius;public String ge

15、tColor() return color;public void setColor(String color) this.color = color;public String toString()if (on)returngetSpeed()+t+getColor()+t+getRadius(); else return fan is off+t+getColor()+t+getRadius();9.11 代数： 2 2 的线性方程public class DemoC public static void main(String args) LinearEquation linearEqu

16、ation1=new LinearEquation(9,4,3,-5,-6,-21); if (linearEquation1.isSolvable()System.out.println(X 是：+linearEquation1.getX()+,tY 是：+linearEquation1.getY(); else System.out.print(The equation has no solution);LinearEquation linearEquation2=new LinearEquation(1,2,2,4,4,5);if (linearEquation2.isSolvable(

17、)System.out.print(X 是： +linearEquation2.getX()+,tY 是：+linearEquation2.getY(); else System.out.print(The equation has no solution);class LinearEquationprivate double a;private double b;private double c;private double d;private double e;private double f;public LinearEquation(double a,double b,double c,double d,double e,doublef) this.a=a;this.b=b;this.c=c;this.d=d;this.e=e;this.f=f;public double getA() return a;public double getB() return b;public double g