Answer:
import java.util.Scanner;
public class Program
{
   public static void main(String [] Args)
   {
       int totalAGrades = 0, totalBGrades = 0, totalCGrades = 0, totalDGrades = 0, totalFGrades = 0, counter=0,maximum = 0, minimum = 9999, num, total = 0,smallest = 0,largest = 0;
        Scanner in = new Scanner(System.in);
        System.out.println("Enter exam percentage: ");
        System.out.println("Enter a negative examScore: ");
        int examScore = in.nextInt();
        while(examScore > 0)
        {
          counter++;
          if(examScore < 0){          
              break;}   
          else if(examScore > maximum){      
               maximum = examScore;}
          else if(examScore < minimum)   {   
               minimum = examScore;}
          
           total = total + examScore;  
      
           if(examScore <= 50 && examScore>0)
               smallest = examScore;
               if(examScore > 90 && examScore <=100)
               largest = examScore;
          
       if(examScore>=90 && examScore<=100)
           totalAGrades++;
       else if(examScore>=80 && examScore<=89)
           totalBGrades++;
       else if(examScore>=70 && examScore<=79)
           totalCGrades++;
       else if(examScore>=60 && examScore<=69)
           totalDGrades++;
       else if(examScore>=0 && examScore<=59)
           totalFGrades++;
       examScore = in.nextInt();
      
    } 
       System.out.println("Total number of scores is = " + counter );
       System.out.println("Total Number of each Letter grade : " + counter);
       System.out.println("Percentage of total for each letter grade : ");
           System.out.println("Total number of A grades = "+ totalAGrades);
           System.out.println("Total number of B grades = "+ totalBGrades);
           System.out.println("Total number of C grades = "+ totalCGrades);
           System.out.println("Total number of D grades = "+ totalDGrades);
           System.out.println("Total number of F grades = "+ totalFGrades);
      
       System.out.println("Lowest exam Score is :"+smallest);
       System.out.println("Highest exam Score is :"+largest);
       System.out.println("Average exam Score = "+ (total / counter));
   }
}   
Explanation:
- Get the exam information from user as input and run a while loop until examScore is greater than zero.
- Use conditional statement to check the scores of students and increment the relevant grade accordingly.
- Finally display all the information including grades and scores.