Detecting types
The idea of run-time type identification (RTTI) seems fairly simple at first: it lets you find the exact type of an object when you only have a reference to the base type.
However, the need for RTTI uncovers a whole plethora of interesting (and often perplexing) OO design issues, and raises fundamental questions of how you should structure your programs.
This chapter looks at the ways that Java allows you to discover information about objects and classes at run-time. This takes two forms: “traditional” RTTI, which assumes that you have all the types available at compile-time and run-time, and the “reflection” mechanism, which allows you to discover class information solely at run-time. The “traditional” RTTI will be covered first, followed by a discussion of reflection.
The need for RTTI
