A visitor of types, in the style of the visitor design pattern. Classes implementing this interface are used to operate on a type when the kind of type is unknown at compile time. When a visitor is passed to a type's accept method, the visitXYZ method most applicable to that type is invoked.

Classes implementing this interface may or may not throw a NullPointerException if the additional parameter p is null; see documentation of the implementing class for details.

WARNING: It is possible that methods will be added to this interface to accommodate new, currently unknown, language structures added to future versions of the Java™ programming language. Therefore, visitor classes directly implementing this interface may be source incompatible with future versions of the platform. To avoid this source incompatibility, visitor implementations are encouraged to instead extend the appropriate abstract visitor class that implements this interface. However, an API should generally use this visitor interface as the type for parameters, return type, etc. rather than one of the abstract classes.

R	the return type of this visitor's methods. Use Void for visitors that do not need to return results.
P	the type of the additional parameter to this visitor's methods. Use Void for visitors that do not need an additional parameter.
version	1.5 06/07/31
since	1.6