the method declarations of an interface are by default public abstract because it only makes sense when a class is able to implement these methods. It's not allowed and wouldn't make much sense if you could declare a private method for example because abstract private methods could never get implemented by any concrete class!
Oh sorry... the protected modifier is not an option for interface methods. They can only be public and are implicitly public abstract whether you declare it with these modifiers or not!
@Pratap: You're right, I only explained the technical aspect of interface method declarations because I thought this is what tushartrue wanted to know. Of course you'll usually use a public interface to propagate your public API or contract of your code to other programmers.