What is a deprecated annotation target - implementation, interface or both?

I wonder, if I have to annotate a @Deprecated method at all their occurrences e.g: Interface, Base (Abstract Class) and all the Implementation Classes or is one annotation in the Interface sufficient?

Actually depends of how deprecated classes are used. Deprecate an interface (methods or attributes) is enough if you use good practices (instantiating the interface to use the implementation).

Anyway,

• you cannot ensure / force this practice in other users
• not all compilers/parsers will throw a warning or show javadoc @deprecated tag

  Using the @Deprecated annotation to deprecate a class, method, or field ensures that all compilers will issue warnings when code uses that program element. In contrast, there is no guarantee that all compilers will always issue warnings based on the @deprecated Javadoc tag, though the Sun compilers currently do so. Other compilers may not issue such warnings. Thus, using the @Deprecated annotation to generate warnings is more portable that relying on the @deprecated Javadoc tag.

Resuming: if you want to deprecate a method implementation you must deprecate both, interface and implementation.

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