Program to calculate average of N numbers

Learn to calculate the average of the given N numbers in Java using three different methods. All methods are different based on how they provide the input to the program.

1. Algorithm for calculating the average

In simple words, to calculate the average of N numbers we have to add all the numbers, and then divide their sum by N.

In pseudo-code, we can list the steps needed in the following manner:

Step 1 : Start

Step 2 : sum = 0, i = 0, average = 0, count = 0

Step 3 : i = i + 2

Step 4 : sum = sum + i, count = count + 1

Step 5 : if i <= 10 then go to on step 3, else go to on step 6

Step 6 : average = sum/count

Step 7 : Display "average"

Step 8 : Stop

2. Program to calculate average of numbers entered by user

We can read the user input using Scanner class.

import java.util.Scanner;

public class CalculateAverage 
{
	public static void main(String[] args) 
	{
		System.out.println("How many numbers do you want to enter?");
		Scanner scanner = new Scanner(System.in);
		//this is number of input values user will provide in console
		int count = scanner.nextInt();	
		
		double[] array = new double[count];
		double sum = 0;

		for (int i = 0; i < array.length; i++) {
			System.out.print("Enter input number " + (i + 1) + ": ");
			array[i] = scanner.nextDouble();
		}
		scanner.close();
		
		for (int i = 0; i < array.length; i++) {
			sum = sum + array[i];
		}

		//Get the average here
		double average = sum / count;

		System.out.format("The average is: %.2f", average);
	}
}

Program output:

How many numbers do you want to enter? 5

Enter input number 1: 10.3
Enter input number 2: 20.6
Enter input number 3: 30.9
Enter input number 4: 5
Enter input number 5: 10

The average is: 15.36

3. Program to calculate average of numbers in array

Calculating the average of all numbers in an array is very much similar to the previous program. Here we have an array already populated with numbers.

double[] array = new double[] {1.1, 2.2, 3.3, 4.4, 5.5};
double total = 0;
for (int i = 0; i < array.length; i++) {
	total = total + array[i];
}

//Get the average here
double average = total / array.length;

System.out.format("The average is: %.2f", average);

4. Program to calculate average of numbers in ArrayList

Since Java 8, Stream API has improved the language a lot and has enabled programmers to write complex logic in very less number of lines of code.

To calculate the average of numbers in this list, we can use the average() method from either IntStream or DoubleStream classes.

In below example, mapToDouble() method returns the DoubleStream. Using the DoubleStream.average() we can easily find the average.

List<Double> list = new ArrayList<>(List.of(1.1, 2.2, 3.3, 4.4, 5.5));
		
Double averageValue = list.stream()
			.mapToDouble((x) -> x)
			.average()
			.orElse(Double.NaN);

System.out.println(averageValue);

Happy Learning !!