Sum of ArrayList java

In this article, we will see different options to calculate sum or average of an ArrayList.

Using Looping structures

Here is we are using an enhanced for loop to find the average of given arraylist of integers. However, any looping construct like while, do..while, for loop etc can be used.

package com.test; import java.util.Arrays; import java.util.List; public class ArrayListOperations { public static void main[String[] args] { List list = Arrays.asList[1, 2, 3, 4, 5, 6, 7, 8]; double sum = 0; for [int i : list] { sum += i; } double average = sum / list.size[]; System.out.println["Average = " + average]; } }

Output :
Average = 4.5

You could also use an Iterator or ListIterator for the same.

Here is the code :

List list = Arrays.asList[1, 2, 3, 4, 5, 6, 7, 8]; double sum = 0; Iterator iter1 = list.iterator[]; while [iter1.hasNext[]] { sum += iter1.next[]; } double average = sum / list.size[]; System.out.println["Average = " + average];

Output :

Average = 4.5

Refer more on the iterators in this article :

Iterating a collection using Iterator, ListIterator, ForEach and Spliterator

Using Java 8 Stream

List list = Arrays.asList[1, 2, 3, 4, 5, 6, 7, 8]; OptionalDouble avg = list.stream[].mapToDouble[i -> i].average[]; System.out.println["Average = " + avg.getAsDouble[]];

Output :

Average = 4.5

Using Java 8 IntStream average[] method

List list = Arrays.asList[1, 2, 3, 4, 5, 6, 7, 8]; OptionalDouble avg = list.stream[].mapToInt[Integer::intValue].average[]; System.out.println["Average = " + avg.getAsDouble[]];

Refer following article to know more about other IntSream operations :

Java 8 IntStream operations with examples

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