（2.2-2.12小节）+（2.13-2.17小节）
（2.2-2.12小节）
2.1 （将摄氏温度转换为华氏温度）
import java.util.Scanner;
public class X {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter a degree in Celsius : ");
double Celsius=input.nextDouble();
input.close();//以后要养成好习惯，输入完要记得关input
double Fahrenheit=(9/5)*Celsius+32;
System.out.println(Celsius +" Celsius is " + Fahrenheit + " Fahrenheit " );
}
}
2.2（计算圆柱体的体积）
import java.util.Scanner;
public class X1 {
public static void main(String[] args) {
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();
input.close();
final double PI=3.14159008;
double area=radius*radius*PI;
double volume=area*length;
System.out.println("The area is " + area );
System.out.println("The volume is " + volume);
}
}
2.3（将英尺转换为米）
import java.util.Scanner;
public class X2 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter a value for feet: ");
double feet=input.nextDouble();
input.close();
double meters=1/0.305;
System.out.println(feet + " feet is " + meters + " meters ");
}
}2.4（将磅转换为千克）
import java.util.Scanner;
public class X4 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter a number in pounds: ");
double pounds=input.nextDouble();
input.close();
double kilograms=0.454*pounds;
System.out.println(pounds + " pounds is " + kilograms + " kilograms ");
}
}
*2.5（财务应用程序：计算小费）
import java.util.Scanner;
public class X5 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter th subtotal and a gratuity rate: ");
double subtotal=input.nextDouble();
double gratuityRate=input.nextDouble();
input.close();
double gratuity=(gratuityRate/100)*subtotal;
double total=subtotal+gratuity;
System.out.println("The gratuity is " + "$"+ gratuity + " and total is " + "$" + total );
}
}
**2.6（求一个整数各位数的和）
import java.util.Scanner;
public class X6 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter a number between 0 and 1000: " );
int integer=input.nextInt();
input.close();
int unitsDigit=integer%10;
int tensDigit=(integer/10)%10;
int hundredsDigit=(integer/100)%10;
int sum=unitsDigit+tensDigit+hundredsDigit;
System.out.println("The sum of the digits is " + sum);
}
}
*2.7（求出年数）
暂时不会
*2.8（当前时间）
暂时不会
2.9（物理：加速度）
import java.util.Scanner;
public class X9 {
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();
input.close();
double acceleration=(v1-v0)/t;
System.out.println("The average acceleration is " + acceleration);
}
}2.10（科学：计算能量）
import java.util.Scanner;
public class X10 {
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 initialTemperature=input.nextDouble();
System.out.print("Enter the final temperature : ");
double finalTemperature=input.nextDouble();
input.close();//
double energy=amount*(finalTemperature-initialTemperature)*4184;
System.out.println("The energy needed is " + energy);
}
}2.11（人口统计）
import java.util.Scanner;
public class X11 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter the number of years: ");
int numbers=input.nextInt();
input.close();
int secondsTotal=365*(60*60*24);//一年总共有多少秒
double live=secondsTotal/7;
double dead=secondsTotal/13;
double in=secondsTotal/45;
double population= 312032486 + numbers*(live + in - dead );
System.out.println("The population in " + numbers + " years is " + (int)population);
}
}
2.12（物理：求出跑道长度）
import java.util.Scanner;
public class X12 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter speed and acceleration: ");
double speed=input.nextDouble();
double acceleration=input.nextDouble();
input.close();
double length=Math.pow(speed, 2) / (2 * acceleration) ;
System.out.print("The minimum runway length for this airplane is " + length);
}
}
**2.13（财务应用程序：复制值）
（用循环一起完成了 第五章的编程习题 5.30）
import java.util.Scanner;
public class X13 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter the monthly saving amount : ");
double save=input.nextDouble();
System.out.print(" 请问您想要显示第几个月后的账户值 (1-12)： ");
int number=input.nextInt();
input.close();
double sum=0;
if(number>0 && number<13) {
for(int i=1; i<=number; i++) {
sum= ((sum+save)*(1+0.00417));
}
}
System.out.println("After the " + number +" month, the account value is $" + sum );
}
}
*2.14（医疗应用程序：计算BMI）
import java.util.Scanner;
public class X14 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter weight in pounds (输入的体重以磅为单位):");
double weight=input.nextDouble();
System.out.print("Enter height in pounds (输入的身高以英寸为单位):");
double height=input.nextDouble();
input.close();
double weight1= weight*0.45359237;
double height1= height*0.0254;
double bmi=weight1/Math.pow(height1,2);
System.out.print(" BMI is :" + bmi );
}
}
2.15（几何：两点间的距离）
import java.util.Scanner;
public class X15 {
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();
input.close();
double a=Math.pow(x2-x1,2) + Math.pow(y2-y1,2);
double distance= Math.pow(a, 0.5);
System.out.print("The distance between the two points is " + distance );
}
}
2.16（几何：六边形面积）
import java.util.Scanner;
public class X16 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter the side: ");
double s=input.nextDouble();
input.close();
double area=3*Math.pow(3,0.5) / 2 * Math.pow(s,2);
System.out.print("The area of the hexagon is " + area );
}
}
*2.17（科学：风寒温度）
import java.util.Scanner;
public class X17 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.println("Enter the temperature in Fahrenheit between -58℃F and 41℃F：");
double temperature=input.nextDouble();
System.out.print("Enter the wind speed (>=2) in miles per hour:");
double windSpeed=input.nextDouble();
input.close();
double windChill= 35.74 + 0.6215*temperature - 35.75*Math.pow(windSpeed, 0.16)
+ 0.4275*temperature*Math.pow(windSpeed, 0.16);
System.out.print("The wind chill index is " + windChill);
}
}
2.18（打印表格）
public class X18 {
public static void main(String[] args) {
System.out.println(" a b pow(a,b)");
System.out.println(" 1 2 "+(int)Math.pow(1,2));
System.out.println(" 2 3 "+(int)Math.pow(2,3));
System.out.println(" 3 4 "+(int)Math.pow(3,4));
System.out.println(" 4 5 "+(int)Math.pow(4,5));
System.out.println(" 5 6 "+(int)Math.pow(5,6));
}
}
*2.19（几何：三角形的面积）
import java.util.Scanner;
public class X19 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter three points for a triangle: ");
double x1=input.nextDouble();
double y1=input.nextDouble();
double x2=input.nextDouble();
double y2=input.nextDouble();
double x3=input.nextDouble();
double y3=input.nextDouble();
input.close();
double s1= Math.pow( (Math.pow(x2-x1,2) + Math.pow(y2-y1,2) ) , 0.5 );
double s2= Math.pow( (Math.pow(x3-x1,2) + Math.pow(y3-y1,2) ) , 0.5 );
double s3= Math.pow( (Math.pow(x3-x2,2) + Math.pow(y3-y2,2) ) , 0.5 );
double s=(s1+s2+s3)/2;
double area=Math.pow( s*(s-s1)*(s-s2)*(s-s3) , 0.5);
System.out.print("The area of the triangle is: " + (float)area );
}
}
（2.13-2.17小节）
*2.20（财务应用程序：计算利息）
import java.util.Scanner;
public class X20 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter balance and interest rate (e.g., 3 for 3%):");
double balance=input.nextDouble();
double interestRate=input.nextDouble();
input.close();
Double interest= balance * (interestRate/1200);
System.out.print("The interest is " + interest );
}
}*2.21（财务应用：计算未来投资值）
import java.util.Scanner;
public class X21 {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.print("Enter investment amount:");
double investment=input.nextDouble();
System.out.print("Enter annual interest rate in percentage:");
double annualInterestRate=input.nextDouble();
System.out.print("Enter number of years:");
int years=input.nextInt();
input.close();
double value= investment * Math.pow( (1+annualInterestRate/12/100) , 12*years) ;
System.out.print("Accumulated value is $" + (float)value);
}
}
*2.22（财务应用：货币单位）
略
*2.23（驾驶费用）
略
