Understand the concepts single implementation inheritance, multiple interface inheritance, subtype-supertype relationship, and their implications for object-oriented programming (OOP).
Understand constructor chaining involving this() and super() constructs.
State conversion rules for assigning, casting, and passing references.
Determine at runtime if an object is an instance of a specified reference type (or of this type's subtypes), using the instanceof operator.
Understand polymorphism and dynamic method lookup.