Java語言程序設(shè)計(基礎(chǔ)篇)原書第十一版梁勇第9章課后題答案

1、9.1 設(shè)計一個名為 Rectangle 的類表示矩形 public class Testpublic static void main(String args) Rectangle rectangle1=new Rectangle(4,40);System.out.println("矩形的寬是 "+rectangle1.width+", 高是"+rectangle1.height+",面積是 "+rectangle1.getArea()+"，周長是 "+rectangle1.getPerimeter();Rect

2、angle rectangle2=new Rectangle(3.5,35.9);System.out.print("矩形的寬是 "+rectangle2.width+", 高是 "+rectangle2.height+",面積是 "+rectangle2.getArea()+"，周長是 "+rectangle2.getPerimeter();class Rectangledouble width=1;double height=1;Rectangle()Rectangle(double newWidth,doub

3、le newHeight) width=newWidth; height=newHeight;double getArea() return width*height;double getPerimeter() return (width+height)*2;9.3 使用 Date 類 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);

4、l*=10; public static void printDate(long l, Date date) System.out.println(l + ": " + date.toString();9.4 使用 Random 類public class Test public static void main(String args) Random random=new Random(1000);for (int i=1;i<51;i+)System.out.print(random.nextInt(100)+"t"); if (i%10=0)

5、System.out.println();9.6 秒表public class Test public static void main(String args) StopWatch stopWatch=new StopWatch(); stopWatch.start(); int a = new int100000; for (int i=0;i<100000;i+) ai=(int)(Math.random()*200); count(a); stopWatch.stop();System.out.print(" 測試所用時間為： "+stopWatch.getE

6、lapsedTime()+"ms"); public static void count(int a)int max ;int tmp ;for(int i=0;i<a.length;i+)max = i;for(int j=i+1;j<a.length;j+) if(amax<aj) max = j; if(i!=max) tmp = ai; ai = amax; amax = tmp; class StopWatch private long startTime;private long endTime; StopWatch() startTime =

7、 System.currentTimeMillis(); public void start() startTime = System.currentTimeMillis(); public void stop() endTime = System.currentTimeMillis();public long getElapsedTime() return endTime - startTime;9.7 Accont 類public class DemoA public static void main(String args) Account account=new Account();

8、Scanner in=new Scanner(System.in); System.out.println(" 創(chuàng)建用戶，依次輸入 id、balance、annualInterestRate："); int id=in.nextInt();double balance=in.nextDouble();double annualInterestRate=in.nextDouble(); account.ChuangJian(id,balance,annualInterestRate); System.out.print(" 請輸入取款額： ");int m

9、oney=in.nextInt(); account.withDraw(money); System.out.print(" 請輸入存款額： "); money=in.nextInt(); account.deposit(money); account.Print();class Accountprivate int id;private double balance;private double annualInterestRate;private Date dateCreated;public void Print()System.out.println("

10、余額為： "+balance);System.out.println(" 月利息為： "+getMonthlyInterset();System.out.print(" 開戶日期為： "); getDate();public void ChuangJian()id=0;balance=0;annualInterestRate=0;public void ChuangJian(int id,double balance,double annualInterestRate) this.id=id;this.balance=balance; this

11、.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("

12、; 請輸入更改后的 id、 balance、 annualInterestRate"); 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 annualI

13、nterestRate/12;public double getMonthlyInterset()return getMonthlyInterestRate()*balance;public void withDraw(int moneyOut) balance-=moneyOut;public void deposit(int moneyIn) balance+=moneyIn;9.8 Fan類 public class DemoB public static void main(String args) Fan fan1=new Fan(); fan1.setSpeed(3); fan1.

14、setRadius(10); fan1.setColor("yellow"); fan1.setOn(true);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=

15、1;int MEDIUM=2;int FAST=3;private int speed=SLOW;private boolean on=false;private double radius=5;String 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;

16、public double getRadius() return radius;public void setRadius(double radius) this.radius = radius;public String getColor() return color;public void setColor(String color) this.color = color;public String toString() if (on)return getSpeed()+"t"+getColor()+"t"+getRadius(); else ret

17、urn "fan is off"+"t"+getColor()+"t"+getRadius(); 9.11代數(shù)： 2×2的線性方程public class DemoC public static void main(String args) LinearEquation linearEquation1=new LinearEquation(9,4,3-,5,-6,-21);if (linearEquation1.isSolvable()System.out.println("X 是："+linearEqu

18、ation1.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()System.out.print("X 是： "+linearEquation2.getX()+",tY 是： "+linearEquation2.getY();else System.out.print("The equation has no solution"