Lambda Expressions in Java

The most significant and most anticipated feature of Java was the Lambda Expressions. Java 8 introduced Lambda Expressions in Java on 18th March 2014. Earlier Lambda Expressions were trendy and common in other advanced programming languages like Scala, Python, etc. Java lambda expressions were Java’s initial step towards functional programming.

Java Lambda Expression or Lambda function is simply an unnamed expression or function which is rewritten as a parameter for any other function. Instances of functional interfaces are represented using Lambda expressions in Java. Java Lambda expressions can implement just one abstract function and hence implement functional interfaces.

Lambda expression helps in writing a code in a realistic style. Writing code in a realistic manner is advantageous in the collections framework library.It allows iteration, filtration, and extraction of data. Lambda Expressions also adds functional processing capacity to Java. Single Abstract Methods (SAM) interface can be implemented more concisely and effectively using these Lambda Expressions.

Properties of Lambda Expressions in Java 

As we all know that Lambda expressions in Java are just unnamed and unknown functions. However, it still has numerous subsequent properties: 

  1. Lambda Expressions in Java are anonymous because they do not hold any specific name like every other method would usually have. So, it’s clearly less to write and less to remember about.

  2. In Java Lambda Expressions, there is no necessity to write several boilerplates as we do for anonymous classes.
  • A Java lambda expression can be used to be carried as an argument to any function. Java lambda expressions can also be saved in a variable.
  • Lambda expression in Java can also be imagined as a function because lambda expression is not correlated with a particular class similar to a method is. However, like a method, a lambda expression in Java has a list of parameters. It also has a body and a return type. In addition, Java Lambda Expressions contains a potential list of exceptions that can be thrown at any time during the process is running.

Features of Lambda Expressions in Java

Lambda Expressions in Java are mainly recognized because of their features. These characteristics are as follows:

  1. In Java Lambda Expressions, there is no necessity to declare the type or return type of a parameter. That is because the Java compiler can deduce the type of the parameter by looking at its value (parameter’s value).
  • When the expression body contains only a single statement, then there is no need to use the curly braces in Lambda expressions. 
  • In Java Lambda expressions, parentheses are required only for the multiple parameters. For a single parameter, there is no need to use the parentheses or to declare a parameter inside the parentheses.
  • In a body of a single expression to return a value, then the Java compiler automatically returns that value. If a user wants to show that their expression is returning a value, then curly braces are needed to symbolize that expression.

Syntax of Java Lambda Expressions 

The syntax of lambda expressions in Java consists of three main components. These are:

  • Argument List:The argument list is written inside the brackets in the syntax of Java lambda expressions. This argument list can be empty and can contain parameter or parameters as well.
  • Arrow Token:The arrow token is represented by an arrow ( -> ) in Java lambda expressions. This is used to link the parameters in the argument list to the expression of the body.
  • Body:Java Lambda expression’s body is written just after the arrow token. The body comprises the expressions and statements of the lambda expressions in Java.

There are many types of syntax of the Java lambda expressions. These are:

  • No parameter syntax
  • Single parameter syntax
  • Multi-parameter syntax

Examples of Lambda Expressions in Java 

Main.java

Output:

Main.java

Output:

Main.java

          Output:

Points to Remember


The body expression of a lambda expression in Java can contain zero, one, or more statements.

  • Curly brackets are not necessary when there is a single statement, and the return type of the body expression is identical to that of the anonymous function.
  • Furthermore, curly brackets are necessary when there are multiple statements. In this case, the return type of the anonymous function is void if nothing is returned, and if something is returned, then the return type is the same as the type of the value returned inside the curly brackets.

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