Why are these methods abstract?

[Aj Manch]

I came across the following snippet of code in Ed Roman's EJB book:

public interface javax.ejb.SessionBean
extends javax.ejb.EnterpriseBean
{
    public abstract void setSessionContext(.....) throws...
    public abstract void ejbPassivate() throws ....
...
}

I was wondering what's the purpose of using "abstract" in an interface. Because they are abstract by definition, anyways.
Thanks!

[Alex Iordache]

A mistake, I think.

[Cindy Glass]

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.
Note that a method declared in an interface must not be declared static, or a compile-time error occurs, because static methods cannot be abstract.

[Aj Manch]

Thanks for your replies!
Cindy, just wondering where did you get the above quote from?
TIA

[Cindy Glass]

Sorry, I usually try to include that info.
The Java Language Specification as put out by sun here: http://java.sun.com/docs/books/jls/second_edition/html/jTOC.doc.html
That quote was from http://java.sun.com/docs/books/jls/second_edition/html/interfaces.doc.html#78651