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Java Lambda Expression: What is it? With an example

Colin Shah
Colin Shah
November 3, 2023
Clock icon9 mins read
Calendar iconLast updated November 3, 2023
Banner-Lambda expression

Lambda expressions or Java Lambda Expressions were added to Java 8. They were a significant addition to the language. In this article, we will explore why they were introduced and what their purpose is.

What is the Lambda Expression in Java?

A lambda expression is a short block of code that takes in some input (parameters) and returns a value. You can think of lambda expressions as being like methods. Just like methods, they can take parameters and give us return values. However, unlike regular methods, lambda expressions don't need a name. As a result, they can be implemented right in the body of a method.

  • The lambda expression is a new and important feature of Java that was introduced in Java SE 8. 
  • It provides a concise way to represent an anonymous function, which can be used to implement the functional interface.
  • Lambda expressions can be used to iterate, filter, and extract data from collections.

Why Do We Use Lambda Functions?

You may wonder why we use lambda expressions in Java. There are certain use cases where they can be very useful.

Some people say that makes use of anonymous functions more concise and readable, which is obvious and noticeable, but the primary objective of lambda expressions is functional programming.  By using Lambda expressions, you can write cleaner code, which in turn improves readability by eliminating the need for verbose anonymous inner class declarations.

  • To provide the implementation of a functional interface.
  • To improve readability by writing the code without the need for defining separate named functions. 
  • To reduce the codebase by writing modular code and reusable code
  • To improve the collection libraries, making it easier to iterate through, filter, and extract data from a collection.

1. Functional Interfaces

Lambda expressions provide a convenient way to implement the abstract method of a functional interface directly inline, avoiding the need to create separate classes or instances.

We can take the Java Runnable interface as an example. It has only one abstract method, run().

Take an example of the below code has only one method GiveName defined that makes it a functional interface:

interface interface1{

  String GiveName(String str);


2. Collections and Streams

When working with collections, streams, and other data processing operations, lambda expressions can be used to concisely define transformation and filtering functions.

3. Event Handling

In GUI applications and other event-driven scenarios, lambda expressions can be used to simplify the definition of event listeners and handlers. This is because you can define them inline without the need to create separate classes for each event handler.

4. Parallelism

Lambda expressions are closely associated with Java's Stream API, which can be used for parallel processing of data. Lambda expressions make it easier to specify the operations to be applied to individual elements in a parallelized manner.

5. Functional Programming Concepts

If you are interested in functional programming concepts such as first-class functions, higher-order functions, and closures, lambda expressions can be used to implement these concepts in Java code.

Java Lambda Expression Syntax

The syntax for a lambda function in Java is:

(argument-list) -> {body}

1. Argument-list

It contains the variables that the lambda function will take in. A lambda function can be empty or can take multiple arguments, as follows.

No Parameter Syntax:

() -> {  

//Body of no parameter lambda 


One Parameter Syntax:

(p1) -> { 

 //Body of single parameter lambda  

Two Parameter Syntax:

(p1,p2) -> { 

 //Body of multiple parameter lambda  

2. The Arrow Operator (->)

Lambda expressions introduce the new arrow operator (-> ), which is used to link the arguments list and body of the expression.

3. Body

It contains expressions or statements that the lambda function will execute.

Lambda expression example

Let's take a look at a lambda expression example to solidify our understanding of lambda expressions. In the following code snippet, we'll see how lambdas can be used to achieve a specific task.

import java.util.*;  

public class Test{  

    public static void main(String[] args) {

        List<String> list=new ArrayList<String>();  

        list.add("ankit");    list.add("mayank"); 




    } } 

The lambda expression (n) > System.out.println(n) serves as a method for specifying the desired action on each element of the list. It eliminates the necessity of creating a method implementation, resulting in code that is both more succinct and easier to comprehend.


In this article, we have discussed the concept of Lambda expression, which is sometimes referred to as anonymous or unnamed methods. We hope now you have a clear understanding of what they are and how we use them in a Java program.

If you have any Java development needs, contact us today to collaborate with Brilworks. We are here to assist you in transforming your innovative ideas into reality or advancing your ongoing projects. You can hire Java developers on a project basis to achieve your goals.



1. What are Lambda Expressions?

Lambda expressions are a concise way to define anonymous functions in Java. They provide a lightweight alternative to traditional anonymous inner classes, making code cleaner and more readable.

2. How do I use Lambda Expressions?

Lambdas are typically used with functional interfaces. These interfaces have a single abstract method, and lambda expressions provide the implementation for that method. You can pass lambdas as arguments to methods or assign them to variables.

3. What's the benefit of using Lambda Expressions?

Lambdas offer several advantages. They simplify code by reducing boilerplate associated with anonymous inner classes. They also promote functional programming style, leading to more concise and expressive code, especially when working with collections and streams.

4. What's the syntax for Lambda Expressions?

The basic syntax involves parameters (optional parentheses), an arrow (->), and the function body. You can have zero or more parameters, and the body can be a single expression or a block of statements enclosed in curly braces.

5. Are there any limitations to using Lambda Expressions?

Lambdas can only access final or effectively final local variables from the surrounding scope. This ensures predictable behavior and prevents accidental modification of variables within the lambda.

Colin Shah

Colin Shah

As a lead Java developer with 8+ years of experience, I design and develop high-performance web applications using Java, Spring Boot, Hibernate, Microservices, RESTful APIs, AWS, and DevOps. I'm dedicated to sharing knowledge through blogs and tutorials.

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