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《Java程序设计与数据结构》编程练习答案（第二章）（一）

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

2.1

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a degree in Celsius:");        double c = input.nextDouble();        double h = (9.0/5)*c+32;        System.out.println(c+" Celsius is "+h+" Fahrenheit.");    }}

2.2

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           double pi = 3.141592654;        System.out.print("Enter the radius and length of a cylinder:");        Scanner input = new Scanner(System.in);        double r = input.nextDouble();        double l = input.nextDouble();        double s = r*r*pi;        double v = s*l;        System.out.println("The area is "+s);        System.out.println("The volume is "+v);    }}

2.3

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a value for feet:");        double feet = input.nextDouble();        double meters = feet*0.305;        System.out.println(feet+" feet is "+meters+" meters.");    }}

2.4

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a value in pounds:");        double pounds = input.nextDouble();        double kilograms = pounds*0.454;        System.out.println(pounds+" pounds is "+kilograms+" kilograms.");    }}

2.5

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the subtotal and a gratuity rate:");        double t = input.nextDouble();        double g = input.nextDouble();        double extra = t*g/100.0;        double s = extra+t;        System.out.println("The gratuity is $"+extra+" and total is $"+s+".");    }}

2.6

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a number between 0 and 1000:");        int num = input.nextInt();        int d1 = num%10;        num/=10;        int d2 = num%10;        num/=10;        int s = num+d1+d2;        System.out.println("The sum of the digits is "+s+".");    }}

2.7

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the number of minutes:");        int min = input.nextInt();        int days = min/60/24;        int years = days/365;        days %= 365;        System.out.println(min+" minutes is approximately "+years+" years and "+days+" days.");    }}

2.8

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;        System.out.println("Current time is "+currentHour+":"+currentMinute+":"+currentSecond+" GMT.");    }}

2.9

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter v0, v1, and t:");        double v0 = input.nextDouble();        double v1 = input.nextDouble();        double t = input.nextDouble();        double a = (v1-v0)/t;        System.out.println("The average acceleration is "+a+".");    }}

2.10

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the amount of water in kilograms:");        double m = input.nextDouble();        System.out.print("Enter the initial temperature:");        double it = input.nextDouble();        System.out.print("Enter the final temperature:");        double ft = input.nextDouble();        double q = m*(ft-it)*4184;        System.out.println("The energy needed is "+q+".");    }}

2.11

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the number of years:");        int year = input.nextInt();        double base = 312032486;        int secnum = 365*24*3600;        for(int i=1;i<=year;i++)            base=base+secnum/7.0-secnum/13.0+secnum/45.0;        System.out.println("The population in "+year+" years is "+base+".");    }}

2.12

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter speed and acceleration:");        double v = input.nextDouble();        double a = input.nextDouble();        double l = v*v/(2*a);        System.out.println("The minimum runway length for this airplane is "+l+".");    }}

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