I"m a new Java student and i've got my program working except for one problem help

My programs working now except for one problem when the program asks
you to enter a number and you enter anything other than a number it
outputs the error (Error , please enter the number again) but if it's
on Enter number 1 and i enter a letter like t when it goes back to
Enter a number it counts backward instead of asking to Enter number 1
again and i don't know what to do. I tried adding an i++ statement and
that didn't work. can anyone please help Judith

C:\>java program3JS
How many numbers do you want to enter?
3
Enter number 1
3
Enter number 2
t
Error, please enter the number again.
Enter number 1
t
Error, please enter the number again.
Enter number 0
3
Enter number 1
3
Enter number 2
3
Enter number 3
3
The average is 5.0

C:\>

// Author: Judith Spurlock
// Course: ITSE 2417
// Program No: 3
// Due Date: 10/20/2006
//
// Program Name: program3JS.java

import java.util.Scanner;
import java.util.InputMismatchException;

public class program3JS
{
    public static void main (String[] args)
    {

    // Variable declarations

    boolean error = true;
    double average;
    int sum = 0;
    int n = 0;
    int i = 0;
    int num = 0;

    Scanner keyboard = new Scanner(System.in);

    // Loop until there is no error
    do
    {
        try
        { error = false;
            System.out.println("How many numbers do you want to enter?");
            n = keyboard.nextInt();
            if (n <= 0 )
            throw new Exception ("Number must be greater than 0.");

        }
        catch (Exception e)
        {

        String message = e.getMessage();
        System.out.println(message);
        error = true;

        }
    }
    while (error);

    // Loop through each number and calculate the average

    for ( i = 0; i < n; i ++)
    {
        // Repeat input as long as there is an error
        do
        {
            try
            {
                                error = false;
                System.out.println("Enter number " + (i+1));
                num = keyboard.nextInt();
                            sum += num;

            }
            catch(InputMismatchException e)
            {

            keyboard.nextLine();
            System.out.println("Error, please enter the number again.");
            error = true;
            i ++;
            }

        }
        while (error);
    }

    average = sum/n;

    System.out.println ("The average is " + average);
    }

}