java语言程序设计与数据结构（基础篇）第二章答案

答案为本人自己求解，若有错误，还望海涵并及时告知。如有雷同，纯属巧合。

2.1

import java.util.Scanner;

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

　　

2.2

import java.util.Scanner;

public class Welcome
{
　　public static void main(String[] args)
　　{
　　　　final double PI = 3.1415926;
　　　　Scanner input = new Scanner(System.in);
　　　　System.out.print("Enter the radius and length of a cylinder:");
　　　　double radius = input.nextDouble();
　　　　double length = input.nextDouble();
　　　　double area = radius * radius * PI;
　　　　System.out.println("The area is "+area);
　　　　System.out.println("The volume is "+(area * length));
　　}
}

　　

2.3

import java.util.Scanner;

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

　　2.4

import java.util.Scanner;

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

2.5

 1 import java.util.Scanner;
 2
 3 public class Welcome
 4 {
 5     public static void main(String[] args)
 6     {
 7         Scanner input = new Scanner(System.in);
 8         System.out.print("Enter the subtotal and a gratuity rate:");
 9         int fee = input.nextInt();
10         int rate = input.nextInt();
11         System.out.println("The gratuity is $"+fee * rate / 100.0+" and total is $"+(fee + fee * rate / 100.0));
12     }
13 }

2.6

import java.util.Scanner;

public class Welcome
{
    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 oneP = num % 10;
        int tenP = (num - oneP) % 100 / 10;
        int hunP = (num - oneP - tenP) / 100;
        System.out.println("The sum of the digits is "+(oneP+tenP+hunP));
    }
}

2.7

import java.util.Scanner;

public class Welcome
{
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);
		System.out.print("Enter the number of minutes:");
		long min = input.nextLong();
		long remainingday = min / (24 * 60);
		long day = remainingday % 365;
		long year = remainingday / 365;
		System.out.println(min+" minutes is approximately "+year+" years and "+day+" days");
	}
}

2.8

2.9

import java.util.Scanner;

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

2.10

import java.util.Scanner;

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

2.11

2.12

import java.util.Scanner;

public class Welcome
{
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);
		System.out.print("Enter speed and acceleration:");
		double speed = input.nextDouble(),acceleration = input.nextDouble();
		System.out.println("The mininum runway length for this airplane is "+(speed * speed / (2 * acceleration)));
	}
}

　2.13

2.14

import java.util.Scanner;

public class Welcome
{
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);
		System.out.print("Enter weight in pounds:");
		double weight = input.nextDouble();
		System.out.print("Enter height in inches:");
		double height = input.nextDouble();
		double kg = weight * 0.45359237,m = height * 0.0254;
		System.out.println("BMI is "+(kg / (m * m)));
	}
}

2.15

import java.util.Scanner;

public class Welcome
{
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);
		System.out.print("Enter x1 and y1: ");
		double x1 = input.nextDouble(),y1 = input.nextDouble();
		System.out.print("Enter x2 and y2: ");
		double x2 = input.nextDouble(),y2 = input.nextDouble();
		double distance = Math.pow(Math.pow(x2 - x1,2 ) + Math.pow(y2 - y1, 2),0.5);
		System.out.println("The distance between the two points is "+distance);
	}
}

2.16

import java.util.Scanner;

public class Welcome
{
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);
		System.out.print("Enter the length of the side: ");
		double length = input.nextDouble();
		double area = 3.0 / 2 * Math.pow(3, 0.5) * length *length;
		System.out.println("The area of the hexagon is "+area);
	}
}

2.17

2.18

2.19

2.20

2.21

2.22

2.23