#4 inheritance + cmsc131 review

Question 1

keyword: extends

Answer 1

a class can be defined from an existing class (using key word extends)

Question 2

original class is called

Answer 2

base class, parent class, superclass

Question 3

class defined from original class is called

Answer 3

derived class, child class, subclass

Question 4

what does/can a subclass do

Answer 4

inherits all fields and methods of superclass, can only extend one super class

Question 5

subclass constructor

Answer 5

subclass constructor automatically calls its superclass’ default constructor (if superclass has no default constructor, you get an ERROR)

Question 6

keyword: super

Answer 6

subclass constructor can explicitly invoke a (different) superclass constructor using “super” (it’s okay if superclass doesn’t have a constructor)

Question 7

can a superclass object refer to any (direct or indirect) subclass object

Answer 7

YES! b/c a subclass object is a type of superclass object. A superclass can refer to both a superclass object and a subclass object

Question 8

can a subclass object refer to a superclass object

Answer 8

NO! b/c a superclass is not a type of subclass

Question 9

objectName insanceof className

Answer 9

if true, the object is of type class-name or its (direct or indirect) subclasses

Question 10

objectName.getClass()

Answer 10

returns reference to a class object (can be compared (w/ equals() or == ) to see if objects are from the exact same class(not subclass))