In Basic Algebra, mean is nothing but just an average of all the points and is calculated as a sum of all the numbers divided by the total count. Don’t be surprised if you are asked to write a java program that can calculate mean value of an array of integers.

The interviewer might be trying to test your coding style, clean coding ability and ability to think about the boundary conditions and user errors. As you can see in the program below, I have written the method to be fail proof from null value or an empty integer.

package com.icodejava.blog.datastructure; import java.util.Arrays; /** * @author Kushal Paudyal * www.icodejava.com * Created On - Feb 21, 2014 * Last Modified On - Feb 21, 2014 * * This class can be used to find the mean value in an array */ public class AlgebraMeanFinder { public static void main(String args []) { int [] numbers = {5,5,7,2,3,9,8,9,2,6,7,8,1}; /** * Finding mean number of a valid integer array */ findMeanValue(numbers); /** * Testing for null array */ findMeanValue(null); /** * Passing an empty array */ findMeanValue(new int[] {}); } /** * @param numbers - array of numbers whose mean has to be found * Mean is a simple average value of all numbers. * This method is capable of handling boundary conditions. */ public static double findMeanValue(int[] numbers) { double sum = 0; if (numbers == null || numbers.length < 1) { System.out.println("\nInvalid Input. Returning 0. Input was:" + Arrays.toString(numbers)); return sum; } for (int index = 0; index < numbers.length; index++) { sum += numbers[index]; } double mean = (sum / numbers.length); System.out.println("\nInput Array is: " + Arrays.toString(numbers)); System.out.println("Sum:" + sum + " Count:" + numbers.length + " Mean Value is: " + mean); return mean; } }

Here is the output of this program.

Input Array is: [5, 5, 7, 2, 3, 9, 8, 9, 2, 6, 7, 8, 1] Sum:72.0 Count:13 Mean Value is: 5.538461538461538 Invalid Input. Returning 0. Input was:null Invalid Input. Returning 0. Input was:[]