Java语言程序设计（原书第10版）基础篇 第二章课后答案

以下答案都是自己做的答案，可能会有错误的地方。如果核对的时候有发现有误的，请指导我改正一下！！

2.1（将摄氏温度转换为华氏温度）

package demo2;

import java.util.Scanner;

public class demo01 {

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

   }

}

2.2（计算圆柱体的体积）

package demo2;

import java.util.Scanner;

public class demo02 {

  public static void main(String[] args){
 System.out.println("Enter the radius and length of a cylinder:");
 Scanner input=new Scanner(System.in);
 double radius=input.nextDouble();
 double height=input.nextDouble();
 System.out.println("The area is "+radius*radius*Math.PI+"\n"
  + "The volumme is "+radius*radius*Math.PI*height);
 

  }

}

2.3（将英尺转换为米）

package demo2;

import java.util.Scanner;

public class demo03 {

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

   }

}

2.4（将磅转换为千克）

package demo2;

import java.util.Scanner;

public class demo04 {

  public static void main(String[] args){
  System.out.println("Enter a number in pounds:");
  Scanner input=new Scanner(Sys
4000
tem.in);
  double pounds=input.nextDouble();
  System.out.println(pounds+" pounds is "+pounds*0.454+" kilograms");

  }
}

2.5（财务应用程序：计算小费）

package demo2;

import java.util.Scanner;

public class demo05 {

  public static void main(String[] args){
 System.out.println("Enter the subtotal and a gratuity rate");
  Scanner input=new Scanner(System.in);
  double money=input.nextDouble();
  double rate=input.nextDouble();
  System.out.println("The gratuity is "+money*rate/100+" and total is "+money*(1+rate/100));

  }

}

2.6（求一个整数各位数的和）

package demo2;

import java.util.Scanner;

public class demo06 {

  public static void main(String[] args){
 System.out.println("Enter a number between 0 and 1000:");
  Scanner input=new Scanner(System.in);
  int number=input.nextInt();
  int sum=0;
  while(number!=0){
 int temp=number%10;
 sum+=temp;
 number/=10;
  }
  System.out.println("The sum of the digits is "+sum);

  }

}

2.7（求出年数）

package demo2;

import java.util.Scanner;

public class demo07 {

  public static void main(String[] args){
 System.out.println("Enter the number of minutes:");
  Scanner input=new Scanner(System.in);
  int totolMinutes=input.nextInt();
  //计算总天数
  int totolDay=totolMinutes/(60*24);
  //计算总年数
  int totalYear=totolMinutes/(60*24*365);
  //计算当前的天数
  int currentDay=totolDay%(365);
  System.out.println(totolMinutes+" minutes is approximatelly "+totalYear+" years and "+
  currentDay+" days");

  }

}

2.8（当前时间）

package demo2;

import java.util.Scanner;

public class demo08 {

  public static void main(String[] args){
 System.out.println("Enter the time zone offset to GMT");
 Scanner input=new Scanner(System.in);
 int gmt=input.nextInt();
 //得到总毫秒
 long totalMilliseconds=System.currentTimeMillis();
 //计算总秒数
 long totolSeconds=totalMilliseconds/1000;
 //计算当前的第几秒,商是总分钟数
 long currentSecond=totolSeconds%60;
 //计算总分钟数
 long totalMinutes=totolSeconds/60;
 //计算当前第几分钟,商是总小时数
 long currentMinute=totalMinutes%60;
//计算总小时数
 long totolHours=totalMinutes/60;
//计算当前第几个小时
 long currentHour=totolHours%24;
System.out.println("Current time is "+(currentHour+gmt)+
":"+currentMinute+":"+currentSecond+" GMT");

  }

}

2.9（物理：加速度）

package demo2;

import java.util.Scanner;

public class demo09 {

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

  }

}

2.10（科学：计算能量）

package demo2;

import java.util.Scanner;

public class demo10 {

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

   }

}

2.11（人口统计）

package demo2;

import java.util.Scanner;

public class demo11 {

  public static void main(String[] args){
  Scanner input=new Scanner(System.in);
  System.out.println("Enter the number of yeras:");
  int year=input.nextInt();
  int currentPopulation=312032486;
  //计算总秒数
  final int TOTOL_SECONDS=year*365*24*60*60;
  //出生人口
  int birthPopulation=TOTOL_SECONDS/7;
  //死亡人口
  int deathPopulation=TOTOL_SECONDS/13;
  //移民人口
  int migratePopulation=TOTOL_SECONDS/45;
  //计算总人口
  int TotolPopulation=(currentPopulation+(birthPopulation+migratePopulation-deathPopulation));
  System.out.println("The population in "+year+" year is "+TotolPopulation);

  }

}

2.12（物理：求出跑到长度）

package demo2;

import java.util.Scanner;

public class demo12 {

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

  }

}

2.13（财务应用程序：复利值）

package demo2;

import java.util.Scanner;

public class demo13 {

   public static void main(String[] args){
 Scanner input=new Scanner(System.in);
  System.out.println("Enter the monthly saving amount:");
  final double monthlyRate=0.00417;
  double money=input.nextDouble();
  //每个月定时教的钱
 final  double MONEY=money;
  money=money*(1+monthlyRate);
  //计算第2个月到第6个月的账户值
  for(int i=2;i<=6;i++){
  money=(money+MONEY)*(1+monthlyRate);
  }
  System.out.println("After the sixth month, the account value is $"+money);

   }

}

2.14（医疗应用程序：计算BMI）

package demo2;

import java.util.Scanner;

public class demo14 {

  public static void main(String[] args){
 Scanner input=new Scanner(System.in);
  System.out.println("Enter weight in pounds:");
  double weight=input.nextDouble();
  System.out.println("Enter height in inches:");
  double height=input.nextDouble();
  System.out.println("BMI is "+weight*0.45359237/Math.pow(height*0.0254, 2));

  }

}

2.15（几何：两点间距离）

package demo2;

import java.util.Scanner;

public class demo15 {

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

 }

}

2.16（几何：六边形面积）

package demo2;

import java.util.Scanner;

public class demo16 {

  public static void main(String[] args){
 Scanner input=new Scanner(System.in);
  System.out.println("Enter the side:");
  double size=input.nextDouble();
  System.out.println("The area of the hexaon is "+3*Math.sqrt(3)*Math.pow(size, 2)/2);

  }

}

2.17（科学：风寒温度）

package demo2;

import java.util.Scanner;

public class demo17 {

   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 fahrenheit=input.nextDouble();
  System.out.println("Enter the wind speed (>=2) in miles per hour:"); 
  double speed=input.nextDouble();
  System.out.println("The wind chill index is "
  +(35.74+0.6215*fahrenheit-35.75*Math.pow(speed, 0.16)
  +0.4275*fahrenheit*Math.pow(speed, 0.16))); 

   }

}

2.18（打印表格）

package demo2;

import java.util.Scanner;

public class demo18 {

   public static void  main(String[] args){
  Scanner input=new Scanner(System.in);
  System.out.println("a    b    pow(a,b)");  
  while(input.hasNext()){
  int a=input.nextInt();
  int b=input.nextInt();
  System.out.println(a+"    "+b+"    "+(int)Math.pow(a, b));
  }

   }

}

2.19（几何：三角形的面积）

package demo2;

import java.util.Scanner;

public class demo19 {

  public static void main(String[] args){
  Scanner input=new Scanner(System.in);
  System.out.println("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();
  double a=Math.sqrt(Math.pow(x1-x2, 2)+Math.pow(y1-y2, 2));
  double b=Math.sqrt(Math.pow(x1-x3, 2)+Math.pow(y1-y3, 2));
  double c=Math.sqrt(Math.pow(x2-x3, 2)+Math.pow(y2-y3, 2));
  double s=(a+b+c)/2;
  double area=Math.sqrt(s*(s-a)*(s-b)*(s-c));
  System.out.println("The area of the triangle is "+area);

  }

}

2.20（财务应用程序：计算利息）

package demo2;

import java.util.Scanner;

public class demo20 {

  public static void main(String[] args){
 Scanner input=new Scanner(System.in);
  System.out.println("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（财务应用：计算未来投资值）

package demo2;

import java.util.Scanner;

public class demo21 {

 public static void main(String[] args){
  Scanner input=new Scanner(System.in);
  System.out.println("Enter investment amount:");
  double investmentAmount=input.nextDouble();
  System.out.println("Enter annual interest rate in percemtage:");
  double rate=input.nextDouble();
  System.out.println("Enter number of years:");
  int year=input.nextInt();
  double value=investmentAmount*Math.pow((1+rate/1200), year*12);
  System.out.println("Accumulated value is :"+value);
  

 }

}

2.22（财务应用：货币单位）

package demo2;

import java.util.Scanner;

public class demo22 {

  public static void main(String[] args){
  Scanner input=new Scanner(System.in);
  System.out.println("Enter an amount in int, for example 1156:");
  int amount=input.nextInt();
  //计算多少张美元
  int numberOfOneDollars=amount/100;
  amount=amount%100;
  //计算多少张二角五分
  int numberOfOneQuarters=amount/25;
  amount=amount%25;
  //计算多少张一角
  int numberOfOneDime=amount/10;
  amount=amount%10;
  //计算多少张五分
  int numberOfOneNickel=amount/5;
  amount=amount%5;
  //计算多少张一分
  int numberOfOnePenny=amount/1;
  System.out.println("Your amount "+amount+" consists of");
  System.out.println("    "+numberOfOneDollars+" dollars");
  System.out.println("    "+numberOfOneQuarters+" quarter");
  System.out.println("    "+numberOfOneDime+" dime");
  System.out.println("    "+numberOfOneNickel+" nickel");
  System.out.println("    "+numberOfOnePenny+" penny");

  }

}

2.23（驾驭费用）

package demo2;

import java.util.Scanner;

public class demo23 {

  public static void main(String[] args){
  Scanner input=new Scanner(System.in);
  System.out.println("Enter the driving distance:");
  double distance=input.nextDouble();
  System.out.println("Enter miles per gallon:");
  double miles=input.nextDouble();
  System.out.println("Enter price per align gallon:");
  double price=input.nextDouble();
  double cost=(distance/miles)*3.55;
  System.out.println("The cost of driving is :"+cost);

  }

}