I have a set of POJOs with a common superclass. Those are stored in a two-dimensional array of type superclass. Now, I want to obtain an object from the array and use methods of the subclass. This means I have to cast them to the subclass. Is there a way to do this without using instanceof?
Update: As a concrete example: http://obviam.net/index.php/the-mvc-pattern-tutorial-building-games/ See: "Add new actions (attack) when an enemy is clicked"
If you know they're of the subclass type, then just cast them directly without an instanceof check.
But putting them in a superclass-typed array is telling the compiler to discard the information that they're actually of the subclass type. Either your superclass should expose those methods (perhaps as abstract), or your array should be of the subclass type (so you're not telling the compiler to forget the actual type of the objects), or you'll have to suck it up and do the cast (possibly with the instanceof test).
The only other notable alternative is that you might experiment with the visitor pattern, which passes an action to the object and lets the object decide what to do with it. That lets you override classes to ignore or perform the actions based on their runtime type.