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What are lambda expressions and how to use them in Java?

Java 8Object Oriented ProgrammingProgramming

Lambda expressions are introduced in Java 8. These are used primarily to define inline implementation of a functional interface, i.e., an interface with a single method only.

Lambda expression eliminates the need of anonymous class and gives a very simple yet powerful functional programming capability to Java.

Syntax

parameter -> expression body

Example

Live Demo

public class Java8Tester {
   public static void main(String args[]) {
      Java8Tester tester = new Java8Tester();
      //with type declaration
      MathOperation addition = (int a, int b) -> a + b;
      
      //without type declaration
      MathOperation subtraction = (a, b) -> a - b;
      
      //with return statement along with curly braces
      MathOperation multiplication = (int a, int b) -> { return a * b; };
      
      //without return statement and without curly braces
      MathOperation division = (int a, int b) -> a / b;
      System.out.println("10 + 5 = " + tester.operate(10, 5, addition));
      System.out.println("10 - 5 = " + tester.operate(10, 5, subtraction));
      System.out.println("10 x 5 = " + tester.operate(10, 5, multiplication));
      System.out.println("10 / 5 = " + tester.operate(10, 5, division));
      
      //without parenthesis
      GreetingService greetService1 = message ->
      System.out.println("Hello " + message);
      
      //with parenthesis
      GreetingService greetService2 = (message) ->
      System.out.println("Hello " + message);
      greetService1.sayMessage("Mahesh");
      greetService2.sayMessage("Suresh");
   }
   interface MathOperation {
      int operation(int a, int b);
   }
   interface GreetingService {
      void sayMessage(String message);
   }
   private int operate(int a, int b, MathOperation mathOperation) {
      return mathOperation.operation(a, b);
   }
}

Output

10 + 5 = 15
10 - 5 = 5
10 x 5 = 50
10 / 5 = 2
Hello Mahesh
Hello Suresh
raja
Samual Sam
Updated on 30-Jul-2019 22:30:20

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