Lecture 2

Learning Outcomes

At the end of this lecture, you’ll be able to:

• Define inheritance and polymorphism and identify them in Java source code.
• Use inheritance to design simple class hierarchies that allow code to be reused for distinct subclasses.
• Explain the relationship between inheritance and type substitution (the idea of a subtype being usable in a context that expects the super type).
• Identify apparent and actual types of objects, and explain the relationship between them.
• Express how type casting works for objects, and differentiate between “Upcasting” and “Downcasting”.
• Distinguish between single, multiple, and multi-level inheritance.
• Explain the relationship between polymorphism and type substitution.
• Distinguish between dynamic (runtime) and static (compile-time) polymorphism.
• Describe how Java’s method dispatch process works.
• Develop examples of compile-time and runtime polymorphism.
• Recognize inheritance must be used to model “is-a” relationship.
• Contrast “is-a” to “has-a” relationships.
• Arrange classes in a simple class diagram that exhibits “is-a”/“has-a” relationships.
• Distinguish method overloading from method overriding.
• Explain how every object in Java has a toString method.