Benefits of using functional programming in Java

 (Originally published in LinkedIn)

Functional programming has been gaining popularity in recent years, and for good reason. It offers several benefits over traditional imperative programming, including improved code readability, easier debugging, and reduced complexity. In this post, we'll explore the benefits of using functional programming in Java, complete with code examples to help you get started.

Let's take a closer look at some code examples to better understand the benefits of functional programming in Java.

1. Improved Code Readability

Here's an example of a functional approach to finding the maximum value in a list of numbers:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
OptionalInt maxValue = numbers.stream().mapToInt(Integer::intValue).max();
System.out.println(maxValue.getAsInt());

As you can see, the code is concise and easy to understand. It's also less prone to errors, as there's no need to worry about complex control structures or mutable state.

Easier Debugging

Here's an example of a functional approach to finding the longest word in a list of words:

List<String> words = Arrays.asList("apple", "banana", "cherry", "date");
Optional<String> longestWord = words.stream().max(Comparator.comparingInt(String::length));
System.out.println(longestWord.get());

In this example, there are no side effects and the function always returns the same result for the same input. This makes it easier to debug and test the code, as you can be confident that it's working as expected.

Reduced Complexity

Here's an example of a functional approach to finding the average length of words in a list:

List<String> words = Arrays.asList("apple", "banana", "cherry", "date");
double averageLength = words.stream().mapToInt(String::length).average().getAsDouble();
System.out.println(averageLength);

In this example, the code is broken down into smaller, more manageable parts. This makes it easier to understand and maintain the code, as well as to add new features.

Increased Productivity

Here's an example of a functional approach to finding the number of words in a list that start with a specific letter:

List<String> words = Arrays.asList("apple", "banana", "cherry", "date");
long count = words.stream().filter(word -> word.startsWith("a")).count();
System.out.println(count);

In this example, the use of higher-order functions allows you to write reusable code that can be easily combined and reused. This reduces the amount of code you need to write and increases your overall productivity.

Improved Performance

Here's an example of a functional approach to calculating the sum of squares of all the numbers in a list:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
int sumOfSquares = numbers.parallelStream().mapToInt(n -> n * n).sum();
System.out.println(sumOfSquares);

In this example, the use of parallel streams makes it easier to write parallel and concurrent code, leading to improved performance and scalability, especially for large-scale applications.

In conclusion, these code examples demonstrate how functional programming can improve the readability, debugability, and maintainability of your code, as well as increase your productivity and improve performance. Whether you're just starting out or are an experienced Java developer, it's well worth.