What is a Java lambda function?
Educative Answers TeamA lambda function is a function declared without a name. Lambda functions have been incorporated in Java 8 to provide preliminary support for functional programming. They are primarily used to implement the abstract function of a functional interface.
Quick reminder: A functional interface is a class with one, and only one, abstract function.
Benefits of using lambda functions include improved readability and less boilerplate code.
Syntax
- There can be zero or more arguments. If there is more than one argument, then they need to be enclosed inside the parenthesis.
- If the function body consists of only one line, then curly braces are optional.
- The function body may or may not contain a return statement.
Examples
The example below goes over the basic syntax again.
//convert to upper case and print elements of a list
import java.util.*;
class HelloWorld {
public static void main( String args[] ) {
List <String> myString = new ArrayList<>();
myString.add("Hello");
myString.add("World");
//using a lambda function inside the forEach
myString.forEach(word -> System.out.println(word.toUpperCase()));
}
}A functional interface will be used in the following examples to demonstrate how the usage of lambda functions result in cleaner code.
1. Traditional use
// Printing the name of the person along with Hello
interface Hello {
void with_name(String Name);
}
class HelloWorld {
public static void main(String args[]) {
String name = "Bob";
Hello obj = new Hello() {
public void with_name(String Name){
System.out.println("Hello " + Name);
}
};
obj.with_name(name);
}
}2. Using a lambda function
Using explicit argument types
Here we have explicitly mentioned that the Name would be a string:
interface Hello {
void with_name(String Name);
}
class HelloWorld {
public static void main(String args[]) {
String name= "Bob";
Hello obj = (String Name) ->
System.out.println("Hello " + Name);
obj.with_name(name);
}
}Using implicit argument types
Here compiler would infer from the method declaration that the Name would be a string:
interface Hello {
void with_name(String Name);
}
class HelloWorld {
public static void main(String args[]) {
String name= "Bob";
Hello obj = (Name) ->
System.out.println("Hello " + Name);
obj.with_name(name);
}
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