Understand the concept of a class hierarchy

Use the 'extends' keyword to establish inheritance relationships

Recognize that a class can extend only one superclass

Explain the 'is-a' relationship in inheritance

Understand that all classes implicitly extend Object if no other superclass is specified

Identify common attributes and behaviors to place in a superclass

Discuss the trade-offs between inheritance and composition

Understand the implications of the 'Object' class being the root of all class hierarchies

Implement and use abstract classes in a class hierarchy

Understand that constructors are not inherited

Know that every constructor must call a superclass constructor as its first action

Use the 'super' keyword to explicitly call a superclass constructor

Understand implicit calls to the no-argument superclass constructor

Explain the process of constructor chaining up to Object

Handle complex initialization scenarios in multi-level inheritance

Understand that subclasses inherit public methods from superclasses

Override inherited methods in subclasses

Use the '@Override' annotation when overriding methods

Call the superclass version of an overridden method using 'super'

Understand the rules of method overriding (e.g., return type covariance)

Discuss the implications of overriding methods like equals() and hashCode()

Understand that a subclass object can be used wherever a superclass object is expected

Use superclass reference variables to refer to subclass objects

Explain what “polymorphism” means.

Explain how polymorphism allows for code flexibility and extensibility

Understand the difference between compile-time and run-time types

Discuss the implications of polymorphism on method invocation

Understand the concept of dynamic method dispatch

Understand that overridden methods are called based on the actual object type, not the reference type

Recognize that only instance methods can be overridden

Explain how polymorphism works with method overriding

Understand the difference between method overriding and method overloading

Discuss the implications of polymorphism on system design

Understand how polymorphism supports the 'Open-Closed Principle' in OOP