Writing your first lambda

What is a lambda expression?

Java is an object-oriented language. By introducing lambdas in Java 8, the authors of Java tried to add elements of functional programming in Java. Now you might be wondering what the difference between object-oriented programming and functional programming is?

In object-oriented programming, objects and classes are the main entities. If we create a function then it should exist within a class. A function has no meaning outside the scope of the class object.

In functional programming, functions can exist outside the scope of an object. We can assign them to a reference variable and we can also pass them to other methods as a parameter.

A lambda expression is just an anonymous function, i.e., a function with no name and that is not bound to an identifier. We can pass it to other methods as parameters, therefore, using the power of functional programming in Java.

How to write a lambda expression

It might be difficult to understand what lambda is and how to write a lambda without looking at an example. So, let’s look at an example first, and then we will revisit what we just read.

In the below example, we have a functional interface called Greeting. There are two classes HindiGreeting and EnglishGreeting that implement this interface.