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OO Concepts Quiz 9

The quiz below tests your knowledge of the material learnt in OO Concepts - Lesson 9 - Polymorphism.

Question 1 : What is required to use polymorphism?
- We need to have an inheritance hierarchy to use polymorphism, although abstracting out generic methods to force implementation in subclasses helps to enforce it.
Question 2 : What do we use in the declaration of an object to enable polymorphism?
- We use the supertype of the object we are creating
Question 3 : What are used for polymorphism?
- <i>overridden</i> instance methods are used in polymorphism.
Question 4 : We use overloaded methods in polymorphism?
- We DO NOT use <i>overloaded</i> methods in polymorphism we use <i>overridden</i> methods.
Question 5 : What is the following code snippet an example of?

public class A {
    public static void aClassMethod() {
public class B extends A {
    public static void aClassMethod() {
- This is an example of <i>hiding</i>.
Question 6 : We can make the arguments to our methods polymorphic?
- We CAN make the arguments to our methods polymorphic.
Question 7 : What is the dynamic selection of overridden methods at runtime based on the actual object type, rather than the reference type known as?
- This concept is known as <i>virtual method invocation</i>.
Question 8 : We can invoke a static supertype method from a non-static subtype method?
- We CANNOT invoke a static <i>supertype</i> method from a non-static <i>subtype</i> method as our instance methods know nothing of static members and this will not compile anyway.
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What's Next?

In the next quiz we take a first look at interfaces.