《Java语言程序设计与数据结构》编程练习答案（第二章）（二）

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

2.13

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the monthly saving amount:");        double m = input.nextDouble();        double sum = 0.0;        for(int i=0;i<6;i++)            sum = (m+sum)*(1+0.00417);        System.out.println("After the sixth month, the account value is $"+sum+".");    }}

2.14

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter weight in pounds:");        double pounds = input.nextDouble();        System.out.print("Enter height in inches:");        double inches = input.nextDouble();        double bmi = pounds*0.4535927/(inches*inches*0.0254*0.0254);        System.out.println("BMI is "+bmi+".");    }}

2.15

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter x1 and y1:");        double x1 = input.nextDouble();        double y1 = input.nextDouble();        System.out.print("Enter x2 and y2:");        double x2 = input.nextDouble();        double y2 = input.nextDouble();        double d = Math.pow((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1),0.5);        System.out.println("The distance between the two points is "+d+".");    }}

2.16

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the length of the side:");        double s = input.nextDouble();        double a = 3*Math.pow(3,0.5)/2*s*s;        System.out.println("The area of the hexagon is "+a+".");    }}

2.17

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the temperature in Fahrenheit:");        double ta = input.nextDouble();        System.out.print("Enter the wind speed (>=2) in miles per hour:");        double v = input.nextDouble();        double twc = 35.74+0.6215*ta-35.75*Math.pow(v,0.16)+0.4275*ta*Math.pow(v,0.16);        System.out.println("The wind chill is "+twc);    }}

2.18

public class book {
       public static void main(String[] args)    {
           System.out.println("a    b    pow(a,b)");        for(int i = 1;i <= 5;i++)            System.out.println(i+"    "+(i+1)+"    "+(int)Math.pow(i,i+1));    }}

2.19

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.println("Enter the coordinates of three points separated by spaces");        System.out.print("like x1 y1 x2 y2 x3 y3:");        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 s1 = Math.pow((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2),0.5);        double s2 = Math.pow((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3),0.5);        double s3 = Math.pow((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3),0.5);        double s = (s1+s2+s3)/2;        double a = Math.pow(s*(s-s1)*(s-s2)*(s-s3),0.5);        System.out.println("The area of the triangle is "+a);    }}

2.20

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter balance and interest rate:");        double balance = input.nextDouble();        double rate = input.nextDouble();        double interest = balance*(rate/1200);        System.out.println("The interest is "+interest);    }}

2.21

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter investment amount:");        double amount = input.nextDouble();        System.out.print("Enter annual interest rate in percentage:");        double ar = input.nextDouble();        System.out.print("Enter number of years:");        int y = input.nextInt();        double fv = amount*Math.pow(1+ar/1200,y*12);        System.out.println("Future value is $"+fv);    }}

2.22

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter an amount in int, for example 114514:");        int amount = input.nextInt();        int old = amount;        int numberOfOneDollars = amount/100;        amount%=100;        int numberOfQuarters = amount/25;        amount%=25;        int numberOfDimes = amount/10;        amount%=10;        int numberOfNickles = amount/5;        amount%=5;        int numberOfPennies = amount;        System.out.println("Your amount "+old+" consists of");        System.out.println("    "+numberOfOneDollars+" dollars");        System.out.println("    "+numberOfQuarters+" quarters");        System.out.println("    "+numberOfDimes+" dimes");        System.out.println("    "+numberOfNickles+" nickels");        System.out.println("    "+numberOfPennies+" pennies");    }}

2.23

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the driving distance:");        double distance = input.nextDouble();        System.out.print("Enter miles per gallon:");        double youhao = input.nextDouble();        System.out.print("Enter price per gallon:");        double youjia = input.nextDouble();        double price = distance/youhao*youjia;        System.out.println("The cost of driving is $"+price);    }}