Java 8 – Lambda Expression

Lambda Expression in Java 1.8 version

It is introduced in Java ecosystem to bring benefits of Functional programming concepts. Let us look at attributes about it,

• It is an anonymous function or nameless i.e.; a method without name
• Return type is not required, as it could be inferred during course of program execution
• Absolutely not required to mention access-modifiers, as it will be local to where it is declared/defined. But declaring doesn’t result into any error.

So what is actually required to identify a Lambda expression,

• arguments lists, if any otherwise empty parenthesis ( )
• execution part or logic or body or set of correct java statement

Lambda expression syntax

(argument list)->{function_body};

Where,

• argument lists is number of input arguments or parameter
• function body (method implementation) is set of Java statement within curly braces
• And there is special symbol for Lambda expression that is hyphen followed by greater than sign i.e.; ->
  Example – (argument_list) -> {method_body};
• There are certain rules regarding above syntax (->) which we will discuss at the end of this topic

Lambda Expression consists following things only,

• input arguments list inside parenthesis
• method body within curly braces

@FunctionalInterface

interface DemoInterface {

    public void display();

}

 

public class TestLambdaExpression {

 

    // main method

    public static void main(String[] args) {

 

        // Lambda Expression equivalent for above method

        DemoInterface d = () -> System.out.println("Hello World");

 

        // how to invoke Lambda Expression -> Functional Interface

        d.display();

    }

}