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Lambda Expression in Java

By: kalaiarasanpandi

7 July 2025 at 16:04

In Java, Lambda expressions basically express instances of functional interfaces.

Lambda Expressions in Java are the same as lambda functions which are the short block of code that accepts input as parameters and returns a resultant value.

Functionalities of Lambda Expression in Java

Lambda Expressions implement the only abstract function and therefore implement functional interfaces lambda expressions are added in Java 8 and provide the below functionalities.

Enable to treat functionality as a method argument, or code as data.
A function that can be created without belonging to any class.
A lambda expression can be passed around as if it was an object and executed on demand.

// A sample functional interface (An interface with
// single abstract method
interface FuncInterface
{
    // An abstract function
    void abstractFun(int x);
 
    // A non-abstract (or default) function
    default void normalFun()
    {
       System.out.println("Hello");
    }
}
 
class Test
{
    public static void main(String args[])
    {
        // lambda expression to implement above
        // functional interface. This interface
        // by default implements abstractFun()
        FuncInterface fobj = (int x)->System.out.println(2*x);
 
        // This calls above lambda expression and prints 10.
        fobj.abstractFun(5);
    }
}

Output:

Lambda Expression Syntax

lambda operator -> body

Reference:

https://www.geeksforgeeks.org/java/lambda-expressions-java-8/