Java 8 Lambda Expressions Tutorial. Lambda Expression Java

Java 8 Lambda Expressions Tutorial with Examples By Viral Patel on January 29, 2014 Java is a first-class object-oriented language. With the exception of primitive data types, everything in Java is an object. Even an array is an Object. Every class creates instances that are objects. There is no way of defining just a function / method which stays in Java all by itself. There is no way of passing a method as argument or returning a method body for that instance. Since the old days of Swing, we always had written anonymous classes if we wanted to pass some functionality to any method.

Functions are first class citizens in a functional programming language. They exists on their own. You can assign them to a variable and pass them as arguments to other functions. JavaScript is one of the best example of an FP language. 

A closure is a function or reference to a function together with a referencing environment — a table storing a reference to each of the non-local variables of that function. Closest thing that Java can provide to Closure is Lambda expressions. 

A lambda expression is an anonymous function (not 100% true for Java but lets assume it for time being). Simply put, it’s a method without a declaration, i.e., access modifier, return value declaration, and name.

It’s a shorthand that allows you to write a method in the same place you are going to use it. Especially useful in places where a method is being used only once, and the method definition is short. It saves you the effort of declaring and writing a separate method to the containing class.

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