Question

Drivers are concerned with the mileage

obtained by their automobiles. One driver has kept track of

several trips by recording miles driven and gallons used for

each trip. Develop a java program that uses a while statement

to input the miles driven and gallons used for each trip. The

program should calculate and display the miles per gallon

obtained for each trip and print the combined miles per gallon

obtained for all tankfuls up to this point.

Enter miles driven (-1 to quit): 287

Enter gallons used: 13

MPG this trip: 22.076923

Total MPG: 22.076923

Enter miles driven (-1 to quit): 200

Enter gallons used: 10

MPG this trip: 20.000000

Total MPG: 21.173913

Enter the miles driven (-1 to quit): 120

Enter gallons used: 5

MPG this trip: 24.000000

Total MPG: 21.678571

Enter the miles used (-1 to quit): -1

Answer 1

(If you still have any doubts regarding this answer please comment I will definitely help)

Key points to remember:

1. In the printing of MPG and Total_MPG we will get many digits after decimal point. But we need only upto 6 decimal places so we will use
2. String.format("%.6f", Total_MPG) and String.format("%.6f",MPG) to get o/p upto 6 decimal places
3. Total_MPG is equal to sum of all miles / sum of gallons upto that point. That is why in every iteration we are summing the miles and the gallons

Code Explanation:

• Import the required packages
• java.lang.*, java.util.*,java.io.*;
• Create a class with any name. Class name and your file name should be same.
• Inside the class create main function
• declare MPG and Total_MPG as double variables
• declare miles, gallons, Total_miles, Total_gallons as int variables and initialize Total_miles, Total_gallons to 0
• Create an object sc by using Scanner class present in util package
• Use an infinite while loop
• As to enter miles. If miles is -1 then break the loop
• else add miles to Total_miles
• Then ask to enter gallons
• add gallons to Total_gallons.
• Calculate MPG = miles/gallons and print it
• Then calculate Total_MPG = Total_miles / Total_gallons and print it.
• The loop iterates until we enter miles is -1. If -1 is entered loop exists and program stops running.

Code:

import java.lang.*;
import java.util.*;
import java.io.*;
public class Main
{
   public static void main(String[] args)
   {
  
   double MPG, Total_MPG;
   int gallons, miles, Total_miles = 0, Total_gallons = 0;
   Scanner sc = new Scanner(System.in);
       while(true)
       {
       System.out.print("Enter miles driven (-1 to quit): ");
       miles = sc.nextInt();
       if(miles == -1)
       break;
       Total_miles = Total_miles + miles;
       System.out.print("Enter gallons used: ");
       gallons = sc.nextInt();
       Total_gallons = Total_gallons + gallons;
       MPG = (double) miles/gallons;
       System.out.printf("MPG this trip: "+String.format("%.6f", MPG));
       Total_MPG = (double) Total_miles/Total_gallons;
       System.out.printf("\nTotal MPG: "+String.format("%.6f", Total_MPG)+"\n");
       }
   }
}

Sample O/P1:

Enter miles driven (-1 to quit): 287                                                                                            

Enter gallons used: 13                                                                                                          

MPG this trip: 22.076923                                                                                                        

Total MPG: 22.076923                                                                                                            

Enter miles driven (-1 to quit): 200                                                                                            

Enter gallons used: 10                                                                                                          

MPG this trip: 20.000000                                                                                                        

Total MPG: 21.173913                                                                                                            

Enter miles driven (-1 to quit): 120                                                                                            

Enter gallons used: 5                                                                                                           

MPG this trip: 24.000000                                                                                                        

Total MPG: 21.678571                                                                                                            

Enter miles driven (-1 to quit): -1  

Sample O/P2:

Enter miles driven (-1 to quit): 155                                                                                          

Enter gallons used: 20                                                                                                        

MPG this trip: 7.750000                                                                                                       

Total MPG: 7.750000                                                                                                           

Enter miles driven (-1 to quit): 257                                                                                          

Enter gallons used: 30                                                                                                        

MPG this trip: 8.566667                                                                                                       

Total MPG: 8.240000                                                                                                           

Enter miles driven (-1 to quit): -1

Code Screenshot:

Sample O/P1 screenshot:

Sample O/P2 screenshot: