Probability of N Set of Unions start

import java.util.Scanner;

public class UnionNSets
{
    public static void main(String[] args)
    {
        Scanner keyboard = new Scanner(System.in);
        int i;
        int size;
        double totalProbability = 0;
        double probArray[];

        System.out.println("This only works for 3-set unions atm");
        System.out.print("Please enter the size of the array: ");
        size = keyboard.nextInt();
        probArray = new double[size];

//Gathering input
        for (i = 0; i < size; i++)
        {
            System.out.print("Please enter element array[" + i + "]: ");
            probArray[i] = keyboard.nextDouble();
        }

        totalProbability += calcOnes(probArray, size);
        totalProbability -= calcTwos(probArray, size);
        totalProbability += calcThrees(probArray, size);

        System.out.println("Probability of " + size + "-set union: " + totalProbability);
    }

//Sums the initial probabilities
    public static double calcOnes(double[] probArray, int size)
    {
        double result = 0;
        for (int i = 0; i < size; i++)
        {
            result+= probArray[i];
        }
        return result;
    }

//Subtracts every intersection of pairs
    public static double calcTwos(double[] probArray, int size)
    {
        double result = 0;
        for (int i = 0; i < size - 1; i++)
        {
            for (int j = i + 1; j < size; j++)
            {
                result+= probArray[i] * probArray[j];
            }
        }
        return result;
    }

//Sums every intersection of three-pairs
    public static double calcThrees(double[] probArray, int size)
    {
        double result = 0;
        for (int i = 0; i < size - 2; i++)
        {
            for (int j = i + 1; j < size - 1; j++)
            {
                for (int k = j + 1; k < size; k++)
                {
                    result+= probArray[i] * probArray[j] * probArray[k];
                }
            }
        }
        return result;
    }
}