Question

As you know, in a java interface, all methods have to be defined as abstract. But when I define a method as not typing abstract, the compiler says it is okay. I know that an abstract method must not have a body. Does a method somewhere in an interface necessarily have a name abstract or not? : What i mean is, what is the difference between:

public interface blabla {

    public void aMethod();


    //or

    public abstract void aMethod();

}

Answer 1

No, marking an interface method as abstract has no meaning and is never required.

All interface methods are implicitly abstract (and public too btw).

From the JLS:

Every method declaration in the body of an interface is implicitly abstract, so its body is always represented by a semicolon, not a block.

Every method declaration in the body of an interface is implicitly public.

For compatibility with older versions of the Java platform, it is permitted but discouraged, as a matter of style, to redundantly specify the abstract modifier for methods declared in interfaces.

It is permitted, but strongly discouraged as a matter of style, to redundantly specify the public modifier for interface methods.

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Related question (+ answer with a historical reference to a statement saying that abstract was once required for interface methods):

• Java abstract interface