Collision between two ArrayList elements

[jeremydouglass]

See also a recent related discussion for examples of interface, and other approaches:

Looping different class instances

Abstract classes and reflection are fine solutions given your constraint (no interface!) but I’m a bit confused about why this is an issue. If you don’t want to map a large method list up from Helper to A / B / C, then don’t. You can still use an interface. Just create an interface Helpful with only one method – Helper getHelper(), which returns the Helper object of that A/B/C object. Your classes A B C each implement that one method which makes them Helpful (class A implements Helpful … clas…