Podcast
Questions and Answers
What is the primary relationship between a subclass and its superclass?
What is the primary relationship between a subclass and its superclass?
What does a subclass inherit from its superclass?
What does a subclass inherit from its superclass?
What can a subclass do in addition to inheriting from its superclass?
What can a subclass do in addition to inheriting from its superclass?
What is a new feature present in the Circle class that is not present in the GeometricObject class?
What is a new feature present in the Circle class that is not present in the GeometricObject class?
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Which of the following classes is a subclass of the GeometricObject class?
Which of the following classes is a subclass of the GeometricObject class?
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What is the symbol used to denote the inheritance relationship between two classes?
What is the symbol used to denote the inheritance relationship between two classes?
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What is the purpose of the keyword extends in the Circle class?
What is the purpose of the keyword extends in the Circle class?
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Why can't we access the data fields color and filled directly in the constructor of the Circle class?
Why can't we access the data fields color and filled directly in the constructor of the Circle class?
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How can we access the private data fields color and filled in the GeometricObject class?
How can we access the private data fields color and filled in the GeometricObject class?
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What is the result of attempting to use the data fields color and filled directly in the constructor of the Circle class?
What is the result of attempting to use the data fields color and filled directly in the constructor of the Circle class?
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What is the relationship between the Circle class and the GeometricObject class?
What is the relationship between the Circle class and the GeometricObject class?
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What happens when the Circle class extends the GeometricObject class?
What happens when the Circle class extends the GeometricObject class?
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What is the keyword used to define a subclass in Java?
What is the keyword used to define a subclass in Java?
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What is the relationship between the Tree and Person classes in terms of inheritance?
What is the relationship between the Tree and Person classes in terms of inheritance?
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Do subclasses inherit constructors from their superclasses?
Do subclasses inherit constructors from their superclasses?
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How can a superclass's constructor be invoked from a subclass?
How can a superclass's constructor be invoked from a subclass?
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What is the syntax to call a superclass's constructor with arguments?
What is the syntax to call a superclass's constructor with arguments?
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What is the rule for using the 'super' keyword in a subclass constructor?
What is the rule for using the 'super' keyword in a subclass constructor?
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What is the first constructor that gets invoked when a new Faculty object is created?
What is the first constructor that gets invoked when a new Faculty object is created?
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What is the output of the statement new Faculty()?
What is the output of the statement new Faculty()?
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What is the purpose of the statement this("(2) Invoke Employee’s overloaded constructor") in the Employee's no-arg constructor?
What is the purpose of the statement this("(2) Invoke Employee’s overloaded constructor") in the Employee's no-arg constructor?
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What is the relationship between the classes Faculty, Employee, and Person?
What is the relationship between the classes Faculty, Employee, and Person?
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What is the order of constructor invocation when a new Faculty object is created?
What is the order of constructor invocation when a new Faculty object is created?
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Why is the no-arg constructor of Employee invoked when a new Faculty object is created?
Why is the no-arg constructor of Employee invoked when a new Faculty object is created?
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What is the main purpose of overriding a method in a subclass?
What is the main purpose of overriding a method in a subclass?
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Why can a private method not be overridden in a subclass?
Why can a private method not be overridden in a subclass?
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What happens when a static method is redefined in a subclass?
What happens when a static method is redefined in a subclass?
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What is the difference between method overloading and overriding?
What is the difference between method overloading and overriding?
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Why can a subclass inherit a static method from its superclass?
Why can a subclass inherit a static method from its superclass?
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What is the purpose of the toString() method in the Circle class?
What is the purpose of the toString() method in the Circle class?
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Study Notes
Constructors and Inheritance
- The
Faculty
class extends theEmployee
class, which in turn extends thePerson
class. - When a new
Faculty
object is created, the constructors ofFaculty
,Employee
, andPerson
are called in that order. - The
Employee
class has an overloaded constructor that takes a string argument, and a no-arg constructor. - The
Person
class has a no-arg constructor.
Superclasses and Subclasses
- A subclass inherits accessible data fields and methods from its superclass.
- A subclass may also add new data fields and methods.
- The
extends
keyword is used to denote the inheritance relationship between two classes. - A subclass and its superclass must have an "is-a" relationship.
- Private data fields in a superclass are not accessible outside the class, but can be accessed/mutated through public accessors/mutators if defined in the superclass.
Using the super
Keyword
- A subclass does not inherit constructors from its superclass.
- A subclass can invoke its superclass's constructors using the
super
keyword. - The syntax to call a superclass's constructor is
super()
orsuper(parameters)
. - The
super
keyword must be the first statement in the constructor.
Overriding vs. Overloading
- Overloading means defining multiple methods with the same name but different signatures.
- Overriding means providing a new implementation for a method in the subclass.
- An instance method can be overridden only if it is accessible.
- A private method cannot be overridden because it is not accessible outside its own class.
- A static method can be inherited, but it cannot be overridden. If a static method defined in the superclass is redefined in a subclass, the method defined in the superclass is hidden.
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Description
This quiz covers the concept of superclasses and subclasses in Java programming, including inheritance relationships, accessible data fields and methods, and the is-a relationship. Learn how a subclass inherits from its superclass and adds new data fields and methods.