public class Main {

	private static boolean fillInput(double[] numbers, String input) {
		if (input == null || input.length() == 0)
			return false;
		String[] s = input.split(" ");
		if (s == null || s.length != 5)
			return false;
		try {
			for (int i = 0; i < s.length; i++) {
				numbers[i] = Double.parseDouble(s[i]);
			}
		} catch (NumberFormatException e) {
			return false;
		}
		return true;
	}

	private static double averageNumbers(double[] numbers) {
		if (numbers == null || numbers.length == 0)
			return 0;

		double total = 0.0;

		for (int i = 0; i < numbers.length; i++) {
			total = total + numbers[i];
		}

		return total / numbers.length;
	}

	public static void main(String[] args) {

		double[] numbers = new double[5];

		String s = null;

		while (!fillInput(numbers, s)) {
			s = JOptionPane.showInputDialog(null,
					"Enter five numbers, use space to separate them.");
		}

		double average = averageNumbers(numbers);

		JOptionPane.showMessageDialog(null, "Average: " + average);
	}

}