About Question enthuware.ocajp.i.v8.2.1283 :

[Rinkesh]

The option 5 would have been valid even if we don't write throws Exception?

[admin]

What happened when you tried it out?

[nkaragulov]

The first option could have been true?
public void add();
because methods declared in an interface have implicit abstract declaration in it.
I think the question could have been more precise.

[admin]

It is quite precise because the problem statement clearly says, "What is the correct declaration for an abstract method 'add' in a class...". So there is no possibility of an interface here.