Write a program that calculates the average of a stream of non-negative numbers. The user can enter as many non-negative numbers as they want, and they will indicate that they are finished by entering a negative number. For this program, zero counts as a number that goes into the average. Of course, the negative number should not be part of the average (and, for this program, the average of 0 numbers is 0). You must use a method to read in the numbers, keep track of the running sum and count, compute the average, and return the average to the main() method. Note that you must use a loop to do this, as you don't know how many numbers the user will enter ahead of time.

import java.util.Scanner;

public class SumOfPostiveNumbers {

      public static void main(String[] args) {

             //scanner object to read input from user

             Scanner input = new Scanner(System.in);

             boolean repeat = true;

             String userChoice;

             double average;

             do

             {

                    //get the average of the set of numbers using getPositiveNumber method

                    average = getPositiveNumber(input);

                    //display the output

                    System.out.printf("The average is: %.2f", average);

                    //prompt and read if user wishes to repeat the process

                    System.out.print("\n\nDo you want to compute another average (y/n)? ");

                    input.nextLine();

                    userChoice = input.nextLine();

                    //if user enters anything other than y, terminate the program

                    if(!(userChoice.equalsIgnoreCase("y")))

                          repeat = false;

                    System.out.println();

             }while(repeat);

      }

      //method that read a stream of integers and returns the average

      public static double getPositiveNumber(Scanner input)

      {

             // Variables for this method

             double inputValue;

             int numberofNumbers;

             numberofNumbers= 1;

             double average;

             average=0;

             double total;

             total= 0;

             //prompt the user to enter a set of numbers

             System.out.printf("Enter a stream of non-negative numbers (negative when finished): ");

             do

             {

                    //read the number

                    inputValue = input.nextDouble();

                    //if the number is not negative

                    if (inputValue >= 0)

                    {

                          //add it to total

                          total = total + inputValue;

                          //compute the average

                          average = total / numberofNumbers;

                          //increment the count of numbers

                          numberofNumbers = numberofNumbers + 1;

                    }

             } while (inputValue>= 0);

             //return the calculates average

             return average;

      }      

}

Explanation:

answertrue;