Inheritance Ch8

Question 1

What word used to create a subclass

Answer 1

Extends

Class BoxWeight extends Box

Question 2

What happens when a superclass reference variable references a subclass object?

Answer 2

It only has access to the superclass parts of the object

Question 3

How subclass gets private data from superclass

Answer 3

Call super() to construct superclass object

super(w,h,d)

Question 4

True or false.

You can only specify one superclass for each subclass.
And super() refers only to the immediate superclass

Answer 4

Truth

Question 5

T/F: super() constructor must be the first line if used in subclass constructor?

Answer 5

True.

Question 6

What happens if subclass has same method and type signature?

Answer 6

It overrides the superclass method

Question 7

Explain abstract class and why use it

Answer 7

Superclass with common traits but that the subclasses must override a method.
abstract class Figure
Isn’t a,b
abstract area()

Subclasses override area when define the shape

Question 8

How do you prevent overriding a method?

Answer 8

final

final void meth()

Question 9

Can you prevent a class from being inherited?

Answer 9

Yes use final
final class Figure

Question 10

Explain the Object class

Answer 10

Object is the superclass to all classes.
All other objects are subclasses of Object

Defines the methods for all objects

GetClass
toString
clone
equals

Question 11

what is inheritance

Answer 11

building on existing classes to create more specialized classes

Question 12

explain the variable visibility in the subclasses if base class is…

public
protected
private
unspecifid

Answer 12

public is accessible by subclass

protected are directly accessible by subclasses only

private are not inherited are not accessible

unspecified are only accessible by classes in same package

Question 13

how would you know if an object is a instance of another object?

Answer 13

user instanceof

if (anAnimal instanceof Dog )
((Dog) anAnimal).bark();
else
System.out.print(“anAnimal cant be cast to a Dog”)

Question 14

What is downcasting and why do it?

Answer 14

making a superclass object and instance of the subclass. Do this to call a method on the subclass.

(dog) myAnimal.bark()

Question 15

What are some guidelines for inheritance structures

Answer 15

look for objects with common attributes and behaviors

factor common items into a single class

determine which subclasses need specialized behaviors

examine groups of subclasses that may exhibit common behaviors

determine which behaviors should be abstract methods

appy the Is-A test