Chapter 11: How to work with inheritance

Question 1

What is inheritance

Answer 1

When inheritance is used, a subclass inherits the fields and methods of a superclass. Then, when you create an object from the subclass, that subclass can use these fields and methods. The subclass can also provide its own fields and methods that extend the superclass, and it can override fields and methods of the superclass by providing new code for them.

Question 2

What is the Object Class

Answer 2

The superclass for all Java classes. In other words, every class automatically inherits the Object class.

Question 3

What are the methods of the Object Class

Answer 3

toString(), equals(Object), getClass(), clone(), hashCode()

Question 4

What are the 4 access modifiers

Answer 4

private - available within the current class
public - available to classes in all packages
protected - available to classes in the same package and to subclasses
no keyword coded - available to classes in the same package

Question 5

How is a subclass created

Answer 5

public class SubclassName extends SuperClassName{}

Question 6

How do you override a method in a subclass

Answer 6

@Override

Question 7

What is polymorphism

Answer 7

is one of the most important features of object-oriented programming and inheritance. Lets you treat objects of different types as if they were the same type by referring to a superclass that’s common to both objects.

Question 8

What is the instanceOf operator

Answer 8

to check whether a variable is an instance of an object.

Question 9

How to assign a superclass to a subclass and vice versa

Answer 9

Book b = new Book();
cast Book object to a product
Product p = b;
cast Product back to a book
Book b2 = (Book) p;

Question 10

How do we test if two objects point to the same memory location

Answer 10

Product product1 = new Product();
Product product2 = product1;
if (product1.equals(product2))

Question 11

How do we test if two objects have the same data

Answer 11

The equals method of the Product class
@Override
public boolean equals(Object object) { }
if (object instanceof Product) { Product product2 = (Product) object; if (code.equals(product2.getCode()) && description.equals(product2.getDescription()) && price == product2.getPrice()) { return true; return false; } } T