Java Lambda Expression: What is it? With an example

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:

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.

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.

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.

Conclusion

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.

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