Java LongStream sum() Method

📘 Premium Read: Access my best content on Medium member-only articles — deep dives into Java, Spring Boot, Microservices, backend architecture, interview preparation, career advice, and industry-standard best practices.

🎓 Top 15 Udemy Courses (80-90% Discount): My Udemy Courses - Ramesh Fadatare — All my Udemy courses are real-time and project oriented courses.

▶️ Subscribe to My YouTube Channel (176K+ subscribers): Java Guides on YouTube

▶️ For AI, ChatGPT, Web, Tech, and Generative AI, subscribe to another channel: Ramesh Fadatare on YouTube

The sum() method in Java, part of the java.util.stream.LongStream interface, is used to calculate the sum of the elements in the stream. This method is useful when you need to quickly find the total of all the long values in the stream.

Table of Contents

1. Introduction
2. sum() Method Syntax
3. Understanding sum()
4. Examples
   • Basic Usage
   • Using sum() with Filtered Streams
5. Real-World Use Case
6. Conclusion

Introduction

The sum() method is a terminal operation that returns the sum of the elements in the stream. It is particularly useful for aggregating long values, such as summing transaction amounts, calculating total scores, or other numerical data.

sum() Method Syntax

The syntax for the sum() method is as follows:

long sum() 

Parameters:

• This method does not take any parameters.

Returns:

• The sum of the elements in the stream as a long.

Throws:

• This method does not throw any exceptions.

Understanding sum()

The sum() method processes the elements of the stream and calculates their sum. Since it is a terminal operation, it consumes the stream and returns the total sum of its elements.

Examples

Basic Usage

To demonstrate the basic usage of sum(), we will create a LongStream and use sum() to calculate the total of its elements.

Example

import java.util.stream.LongStream; public class SumExample { public static void main(String[] args) { LongStream stream = LongStream.of(1L, 2L, 3L, 4L, 5L); // Use sum() to calculate the total sum of the elements long total = stream.sum(); // Print the total sum System.out.println("Total sum: " + total); } } 

Output:

Total sum: 15 

Using sum() with Filtered Streams

This example shows how to use sum() in combination with filtering to calculate the sum of elements that match a specific condition.

Example

import java.util.stream.LongStream; public class SumWithFilterExample { public static void main(String[] args) { LongStream stream = LongStream.of(10L, 20L, 30L, 40L, 50L); // Use sum() to calculate the sum of elements greater than 25 long total = stream.filter(n -> n > 25).sum(); // Print the total sum System.out.println("Total sum of elements greater than 25: " + total); } } 

Output:

Total sum of elements greater than 25: 120 

Real-World Use Case

Calculating Total Revenue

In real-world applications, the sum() method can be used to calculate the total revenue from a stream of transaction amounts.

Example

import java.util.stream.LongStream; public class SumTransactionsExample { public static void main(String[] args) { LongStream transactionAmounts = LongStream.of(1000L, 2000L, 1500L, 3000L, 2500L); // Use sum() to calculate the total revenue long totalRevenue = transactionAmounts.sum(); // Print the total revenue System.out.println("Total Revenue: " + totalRevenue); } } 

Output:

Total Revenue: 10000 

Conclusion

The LongStream.sum() method is used to calculate the sum of the elements in the stream. This method is particularly useful for quickly finding the total of long values in a stream. By understanding and using this method, you can efficiently manage and process streams of values in your Java applications, ensuring that elements are summed as needed.