Question

I have to use a sentinel while loop to complete the following task in a java program, I want to see how this is executed so I can better understand how the sentinel while loop works. Thank you!

Convert Lab 10 from a counter controlled WHILE loop to a sentinel WHILE loop. Do the following:

• Prompts the user to enter a grade or a -1 to quit.
• IF the user entered a -1 THEN
  • Display a message that the User is done entering grades
• ELSE
  • Count each grade as it is entered.
  • Compute a running total of the grades entered.
• END IF
• After the user enters the sentinel of -1, calculate the average of the grades entered.
• When computing the average, make sure that there is no division by zero. Check to make sure the counter is not equal to zero.
• Make sure the sentinel is not counted as a grade.
• Print out a message stating the average of the grades entered.

Include the following:

1. Use a sentinel-controlled WHILE loop that uses a -1 as the sentinel to exit the loop.
   • Before counting the grades, initialize the counter to zero before the while loop begins.
2. While within the body of the ELSE:
   • Within the WHILE loop:
     • Prompt the User to enter a grade or a -1 to quit.
     • IF the input is not a -1 THEN
       • Count the grade.
       • Compute a running total of these grades as they are entered.
     • END IF
   • After the WHILE Loop is done executing, compute the average of all the grades entered. Remember to check to make sure you don't perform a division by zero.

Answer 1

JAVA CODE

import java.util.Scanner; // import Scanner class

// implement driver class GradeCheck
class GradeCheck
{
public static void main(String [] args)
{
int grade,cnt=0,sum=0; // declare integer variables grade,cnt,sum
float average; // declare float variable average
Scanner scr=new Scanner(System.in); // create Scanner class object "scr"

   while(true) // create infinite while loop
   {
       System.out.print("Enter a grade or a -1 to quit: ");
       grade=scr.nextInt(); // read grades

       if(grade==-1) // check grade=-1
       {
           // print this message
           System.out.println("User is done entering grades...");
           break; // terminate while loop
       }
       else{ // else,
           sum+=grade; // compute sum of grades
           cnt++; // increment counter
       }
   } // end of while loop

   if(cnt!=0) // check counter cnt not =0 then,
   {
       average=sum/(float)cnt; // compute average
       System.out.println("Average of the grades: "+average); // print average
    }
} // main end
} // class end

OUTPUTS:

D:\>javac GradeCheck.java

D:\>java GradeCheck
Enter a grade or a -1 to quit: 2
Enter a grade or a -1 to quit: 3
Enter a grade or a -1 to quit: 4
Enter a grade or a -1 to quit: 4
Enter a grade or a -1 to quit: -1
User is done entering grades...
Average of the grades: 3.25

D:\>java GradeCheck
Enter a grade or a -1 to quit: -1
User is done entering grades...

PROGRAM SCREENSHOTS