Welcome -> the Java 8 way

I started my new year by setting up Java 8 in my machine and playing with Lambda Expressions. Lambda expressions have been my favorite feature in C#. You can refer to some of my posts on Lambda expressions here.

Instead of adding more words to the never-ending information on Lambda expressions on the web let’s understand it with an example.
Let’s create an interface called Greetings with just one method like this.

interface Greetings{
   void print(String message);
}

If you want to create an instance of Greetings and invoke the print() method here’s the old way of doing things.

Greetings oldGreetings = new Greetings(){
   public void print(String message){
	System.out.println("Old greetings: " + message);		
  }
};
oldGreetings.print("Welcome 2014");

The output of this code is Old greetings: Welcome 2014. Now, you don’t want to be creating an anonymous inner class for this. Bring in Lambda expressions as shown here.

 Greetings newGreetings = message -> System.out.println("New greetings: " + message);
 newGreetings.print("Welcome 2014");

It cannot get simpler than this. Notice the use of -> in the code. newGreetings is a reference to a dynamically generated anonymous inner class object. When I try to print the class name of newGreetings it gives me Hello2014$$Lambda$1/518248. In other words newGreetings is an instance of what is called a Functional interface in Java 8. Hello2014 is the class with a main method where I created newGreetings. Here’s the complete code.

interface Greetings{
	void print(String message);
}
public class Hello2014{
  public static void main(String[] args){
    Greetings oldGreetings = new Greetings(){
      public void print(String message){
	System.out.println("Old greetings: " + message);		
      }
   };
   oldGreetings.print("Welcome 2014");
   Greetings newGreetings = message -> System.out.println("New greetings: " + message);
   newGreetings.print("Welcome 2014");
   System.out.println(newGreetings.getClass().getName());
 }
}