A Quick Guide to Functional Programming in Java

Java, long known for its verbose syntax, embraced functional programming with Java 8. This paradigm focuses on writing concise, reusable, and immutable functions, making code cleaner and more efficient.

What is Functional Programming?

Functional programming (FP) is all about writing small, isolated functions with no side effects. Key concepts include:

• Immutability: Data doesn’t change after creation.
• Pure Functions: The output depends only on inputs, avoiding side effects.
• Higher-Order Functions: Functions that take or return other functions.
• First-Class Functions: Functions can be treated like variables.

Why Java Adopted FP

Java moved towards FP to improve scalability and maintainability, especially for modern multi-core systems. It reduces common bugs, like unexpected variable changes, by favoring immutability and pure functions.

Core Java FP Features

1. Lambda Expressions: Concise, inline functions like name -> System.out.println(name) eliminate boilerplate code.
2. Functional Interfaces: Interfaces like Function, Predicate, and Consumer allow you to write reusable, function-based logic.
3. Streams API: Enables declarative data processing with methods like filter, map, and reduce.