java for loop sum and average of range

Question

I have calculated the sum of a for loop range, however i do not know how to count and do the average for my solution. It must be done without any ifs. Just the For loop:

//defining the variables
        // Constants & Variables here
int i;
int numStart;
int numEnd;
double sum = 0;
double average=0;
double loopCount=0;
System.out.print("Enter Start number: "); // keep print line open
numStart = console.nextInt();

System.out.print("Enter End number: ");
numEnd = console.nextInt();

        //enter thevalue
        for (i = numStart; i <= numEnd; i++ )
        {
            sum = sum + i;
            loopCount = numEnd - numStart;
            average = sum+1 / i;


        }
        System.out.println();
        System.out.println( "Sum is: " + sum);
        System.out.println();
        System.out.println( "Average is: " + average);
        System.out.println();

Answer 1

Why even use a for -loop. Thanks to Gauss we know the sum of all elements in range [1 , n] is n * (n + 1) / 2 . The number of integers in the range is simply numEnd - numStart + 1 and the average is the sum of all integers in range divided by the number of integers in the range.

So an optimized solution would look like this:

...
//got numStart and numEnd
int sum = numEnd * (numEnd + 1) / 2 - (numStart - 1) * numStart / 2;
int count = numEnd - numStart + 1;
average = sum / count;

Answer 2

    for (i = numStart; i <= numEnd; i++ )
    {
        sum = sum + i;
        loopcount++;
    }
    average = sum / loopcount;

Answer 3

You can do :

for (i = numStart; i <= numEnd; i++ )
                    {
                        sum = sum + i;
                        loopCount = numEnd - numStart;
                        average = sum /(loopCount+1);


                    }

or

for (i = numStart; i <= numEnd; i++ )
                {
                    sum = sum + i;
                    loopcount++;
                }
                average = sum / loopcount;