Java Lambda Expressions

What is Lambda Expressions?

Java 8 introduced Java Lambda Expressions to improve the readability, expressiveness, and conciseness of code. A lambda expression is a block of code that functions similarly to a standard method but is lightweight and simple to use because it doesn't need a specific name. Like a method, it can take parameters as input and output a value.

Developers can write cleaner and more effective code by using lambda expressions, which are primarily used to implement functional interfaces. Simply put, a lambda expression is an unnamed function that focuses on what needs to be done rather than how the code is structured.

The Necessity of Lambda

Lambda expressions are necessary for writing cleaner, simpler, and more effective code. Large blocks of code can be reduced into compact expressions, improving readability and minimizing boilerplate code.

They allow methods to be created without instantiating a class and enable functional programming in Java. Lambdas can be treated as objects, passed as parameters, stored in variables, and reused when needed.

Functional Interface

A functional interface in Java contains only one abstract method. The @FunctionalInterface annotation ensures that the interface follows the functional interface rules. Lambda expressions implement this abstract method.

Functional interfaces may also contain default and static methods without violating their definition.

Syntax of Lambda Expression in Java

A Java lambda expression consists of three main parts: parameters, the arrow operator, and the body.

1. (arguments) -> { body }

2. No arguments:
   () -> System.out.println("Hello");

3. One argument:
   s -> System.out.println(s);

4. Two arguments:
   (x, y) -> x + y

   (x, y) -> {
       System.out.println(x);
       System.out.println(y);
       return x + y;
   }

Lambda Expressions vs Method

Lambda Expressions	Method
It doesn't need a name	Name is necessary
May or may not include parameters	May or may not include parameters
It does not have a return type	It has a return type
Includes body as the main code segment	Code body is just another code segment of the program

In summary

Java Lambda Expressions are unnamed functions that enable functional programming using succinct parameter-arrow-body syntax, simplify code, implement functional interfaces, reduce boilerplate, and improve readability. They were first introduced in Java 8.