《Java语言程序设计与数据结构》编程练习答案（第三章）（三）

英文名：Introduction to Java Programming and Data Structures, Comprehensive Version, 11th Edition

3.24

public class book {
       public static void main(String[] args)    {
           int num = (int)(Math.random()*13);        int dick = (int)(Math.random()*4);        String[] nums = {
   "Ace","2","3","4","5","6","7","8","9","10","Jack","Queen","King"};        String[] dicks = {
   "Clubs","Diamonds","Hearts","Spades"};        System.out.println("The card you picked is "+nums[num]+" of "+dicks[dick]);    }}

3.25

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           System.out.print("Enter x1, y1, x2, y2, x3, y3, x4, y4: ");        Scanner input = new Scanner(System.in);        double x1 = input.nextDouble();        double y1 = input.nextDouble();        double x2 = input.nextDouble();        double y2 = input.nextDouble();        double x3 = input.nextDouble();        double y3 = input.nextDouble();        double x4 = input.nextDouble();        double y4 = input.nextDouble();        double a = y1-y2;        double b = x2-x1;        double c = y3-y4;        double d = x4-x3;        double e = (y1-y2)*x1-(x1-x2)*y1;        double f = (y3-y4)*x3-(x3-x4)*y3;        double jb = a*d-b*c;        if(jb==0)            System.out.println("The two lines are parallel");        else            System.out.println("The intersecting point is at ("+(e*d-b*f)/jb+", "+(a*f-e*c)/jb+")");    }}

3.26

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           System.out.print("Enter an integer: ");        Scanner input = new Scanner(System.in);        int n = input.nextInt();        System.out.println("Is "+n+" divisible by 5 and 6? "+(n%5==0&&n%6==0));        System.out.println("Is "+n+" divisible by 5 or 6? "+(n%5==0||n%6==0));        System.out.println("Is "+n+" divisible by 5 or 6, but not both? "+(n%5==0^n%6==0));    }}

3.27

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           System.out.print("Enter a point's x- and y- coordinates: ");        Scanner input = new Scanner(System.in);        double x = input.nextDouble();        double y = input.nextDouble();        if(x>=0&&x<=200&&y>=0&&y<=100-0.5*x)            System.out.println("The point is in the triangle");        else            System.out.println("The point is not in the triangle");    }}

3.28

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter r1's center x-, y-coordinates, width, and height: ");        double x1 = input.nextDouble();        double y1 = input.nextDouble();        double w1 = input.nextDouble();        double h1 = input.nextDouble();        System.out.print("Enter r2's center x-, y0coordinates, width, and height: ");        double x2 = input.nextDouble();        double y2 = input.nextDouble();        double w2 = input.nextDouble();        double h2 = input.nextDouble();        if((x1+w1/2>=x2+w2/2)&&(x1-w1/2<=x2-w2/2)&&(y1+h1/2>=y2+h2/2)&&(y1-h1/2<=y2-h2/2))            System.out.println("r2 is inside r1");        else if((x2-w2/2>x1+w1/2)||(x2+w2/2
   
    y1+h1/2)||(y2+h2/2
    
     =x1+w1/2)&&(x2-w2/2<=x1-w1/2)&&(y2+h2/2>=y1+h1/2)&&(y2-h2/2<=y1-h1/2))            System.out.println("r1 is inside r2");        else            System.out.println("r2 overlaps r1");    }}

3.29

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter circle's center x-, y-coordinates, and radius: ");        double x1 = input.nextDouble();        double y1 = input.nextDouble();        double r1 = input.nextDouble();        System.out.print("Enter circle2's center x-, y-coordinates, and radius: ");        double x2 = input.nextDouble();        double y2 = input.nextDouble();        double r2 = input.nextDouble();        if(Math.pow((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2),0.5)<=Math.abs(r1-r2))            System.out.println("circle2 is inside circle1");        else if(Math.pow((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2),0.5)<=r1+r2)            System.out.println("circle2 overlaps circle1");        else            System.out.println("circle2 does not overlap circle1");    }}

3.30

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the time zone offset to GMT:");        long offset = input.nextLong();        long totalMilliseconds = System.currentTimeMillis();        totalMilliseconds+=offset*60*60*1000;        long totalSeconds = totalMilliseconds/1000;        long currentSecond = totalSeconds%60;        long totalMinutes = totalSeconds/60;        long currentMinute = totalMinutes%60;        long totalHours = totalMinutes/60;        long currentHour = totalHours%24;        String tail = "AM";        if(currentHour>12)        {
               currentHour-=12;            tail="PM";        }        System.out.println("Current time is "+currentHour+":"+currentMinute+":"+currentSecond+" "+tail);    }}

3.31

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the exchange rate from dollar to RMB: ");        double rate = input.nextDouble();        System.out.print("Enter 0 to convert dollars to RMB and 1 vice versa: ");        int sig = input.nextInt();        double in = 0;        double out = 0;        String moneyType = "";        if(sig==0)            moneyType="dollar";        else if(sig==1)            moneyType="RMB";        else            System.out.println("Incorrect input");        if(sig==0||sig==1)        {
               System.out.print("Enter the "+moneyType+" amount: ");            in = input.nextDouble();            if(sig==0)            {
                   out = in*rate;                System.out.println("$"+in+" is "+out+" yuan");            }            else            {
                   out = in/rate;                System.out.println(in+" yuan is $"+out);            }        }    }}

3.32

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           System.out.print("Enter three points for p0, p1, and p2: ");        Scanner input = new Scanner(System.in);        double x0 = input.nextDouble();        double y0 = input.nextDouble();        double x1 = input.nextDouble();        double y1 = input.nextDouble();        double x2 = input.nextDouble();        double y2 = input.nextDouble();        double result = (x1-x0)*(y2-y0)-(x2-x0)*(y1-y0);        if(result>0)            System.out.println("p2 is on the left side of the line");        else if(result==0)            System.out.println("p2 is on the same line");        else            System.out.println("p2 is on the right side of the line");    }}

3.33

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter weight and price for package 1: ");        double w1 = input.nextDouble();        double p1 = input.nextDouble();        System.out.print("Enter weight and price for package 2: ");        double w2 = input.nextDouble();        double p2 = input.nextDouble();        double av1 = p1/w1;        double av2 = p2/w2;        if(av1

3.34

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter three points for p0, p1, and p2: ");        double x0 = input.nextDouble();        double y0 = input.nextDouble();        double x1 = input.nextDouble();        double y1 = input.nextDouble();        double x2 = input.nextDouble();        double y2 = input.nextDouble();        if((x1-x0)*(y2-y0)-(x2-x0)*(y1-y0)==0&&x2>=x0&&x2<=x1)            System.out.println("("+x2+", "+y2+") is on the line segment from ("+x0+", "+y0+") to ("+x1+", "+y1+")");        else            System.out.println("("+x2+", "+y2+") is not on the line segment from ("+x0+", "+y0+") to ("+x1+", "+y1+")");    }}