Sum of Consecutive Numbers in Array Java

Input: 10, 11, 12, 13, 14, 15

Output: 75

Java Sum of n Consecutive Numbers

package practice.controlflow;

import java.util.Arrays;
public class NConsecutive 
{
    public static void main(String[] args) 
    {
        int array[] = { 10, 11, 12, 13, 14, 15 };
        int length = array.length;
        int firstNum = array[0];
        int lastNum = array[length - 1];
        int totalSum = length * (firstNum + lastNum) / 2;
        System.out.println("Sum of " + Arrays.toString(array) + " is: "
                + totalSum);
    }
}