Implementation within the Interface - Java

Question

We know that we can't implement functions in interfaces in java.

I just tried

public interface InvoiceService {
public static void getData(){
 System.out.print("this is my data");
 }
}

I am able to execute this function, why is it like that? is it because the function is defined as static and static variables can be accessed using class name directly without creating an object?

• Suresh Atta: Which JDK you are using ?
• Danyal Sandeelo: @sᴜʀᴇsʜᴀᴛᴛᴀ it is 1.8
• Suresh Atta: That's a new feature added in 1.8 :)
• Danyal Sandeelo: my whole life is a lie ;-) implementation in interfaces, it brings a new paradigm in java interfaces..
• Suresh Atta: Welcome to Narnia ;)

Answer 1

Because you might be using Java 8. In Java 8 you can add static methods in interfaces as well as default methods. Please read more about static and default methods in Java 8 documentation

• OldCurmudgeon: Good answer - posting some code examples would improve youir chances of upvotes.
• Suresh Atta: @OldCurmudgeon Nope. you can't do that in older versions.
• OldCurmudgeon: @sᴜʀᴇsʜᴀᴛᴛᴀ - Oops! Thanks for the heads-up.
• Jawad: default method is another type of method that is allowed in interfaces in Java8. They contain a body and can be overridden by implemented classes. However static methods cannot be override.
• Suresh Atta: @DanyalSandeelo Did you go through the official doc provided in my answer?

Answer 2

is it because the function is defined as static and static variables can be accessed using class name directly without creating an object?

You are using Java8 it seems and you just implemented a default method

Yes, that method need not to ovveride by any of the implemented classes and belongs to interface.

And yes you need not to create an instance to access it. You can access it by interface name itself.

And since that is a static method you can use that as any normal utility method

From doc again,

If they add them as static methods, then programmers would regard them as utility methods, not as essential, core methods.