Java Program to Find Average of Array

To find the average of an array in Java, sum all elements using a loop and then divide by the number of elements with average = (double) sum / array.length.

Examples

Input[10, 20, 30]

Output20.0

Input[5, 15, 25, 35]

Output20.0

Input[100]

Output100.0

How to Think About It

To find the average, first add all numbers in the array to get the total sum. Then, divide this sum by how many numbers are in the array. This gives the average value.

Algorithm

1

Initialize a variable to hold the sum as 0.

2

Loop through each element in the array and add it to the sum.

3

Divide the sum by the total number of elements in the array.

4

Return or print the result as the average.

Code

java

public class AverageArray {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30, 40, 50};
        int sum = 0;
        for (int num : numbers) {
            sum += num;
        }
        double average = (double) sum / numbers.length;
        System.out.println("Average: " + average);
    }
}

Output

Average: 30.0

Dry Run

Let's trace the array [10, 20, 30, 40, 50] through the code

1

Initialize sum

sum = 0

2

Add first element

sum = 0 + 10 = 10

3

Add second element

sum = 10 + 20 = 30

4

Add third element

sum = 30 + 30 = 60

5

Add fourth element

sum = 60 + 40 = 100

6

Add fifth element

sum = 100 + 50 = 150

7

Calculate average

average = 150 / 5 = 30.0

Iteration	Current Element	Sum
1	10	10
2	20	30
3	30	60
4	40	100
5	50	150

Why This Works

Step 1: Sum all elements

We add each number in the array using a loop to get the total sum.

Step 2: Divide by count

We divide the sum by the number of elements using array.length to find the average.

Step 3: Use double for precision

Casting sum to double ensures the average includes decimals if needed.

Alternative Approaches

Using Java Streams

java

import java.util.Arrays;
public class AverageArray {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30, 40, 50};
        double average = Arrays.stream(numbers).average().orElse(0);
        System.out.println("Average: " + average);
    }
}

This method is concise and uses modern Java features but requires Java 8 or higher.

Using traditional for loop with index

java

public class AverageArray {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30, 40, 50};
        int sum = 0;
        for (int i = 0; i < numbers.length; i++) {
            sum += numbers[i];
        }
        double average = (double) sum / numbers.length;
        System.out.println("Average: " + average);
    }
}

This is a classic approach using index-based loop, useful if you need the index for other logic.

Complexity: O(n) time, O(1) space

Time Complexity

The program loops through all n elements once to sum them, so it runs in O(n) time.

Space Complexity

Only a few variables are used regardless of input size, so space is O(1).

Which Approach is Fastest?

Both the loop and stream methods run in O(n) time; streams add slight overhead but improve readability.

Approach	Time	Space	Best For
For-each loop	O(n)	O(1)	Simple and clear for beginners
Java Streams	O(n)	O(1)	Concise code, modern Java
Index-based loop	O(n)	O(1)	When index is needed for extra logic