Inheritance Flashcards Chapter 9
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Questions and Answers

What is the general class in an inheritance relationship called?

superclass

What is the specialized class in an inheritance relationship called?

subclass

What key word indicates that a class inherits from another class?

extends

What members of a superclass does a subclass not have access to?

<p>private</p> Signup and view all the answers

What key word refers to an object's superclass?

<p>base</p> Signup and view all the answers

In a subclass constructor, when must a call to the superclass constructor appear?

<p>as the very first statement</p> Signup and view all the answers

What is the following an inexplicit call to the superclass's default constructor? super();

<p>super();</p> Signup and view all the answers

What is it called when a method in a subclass has the same signature as a method in the superclass?

<p>overriding</p> Signup and view all the answers

What is it called when a subclass method has the same name as a method in the superclass but a different signature?

<p>overloading</p> Signup and view all the answers

What members of a superclass are accessible to subclasses and classes in the same package?

<p>protected</p> Signup and view all the answers

When a class implements an interface, what must it provide?

<p>all of the nondefault methods that are listed in the interface, with the exact signatures and return types specified</p> Signup and view all the answers

What are fields in an interface?

<p>both final and static</p> Signup and view all the answers

Abstract methods must be what?

<p>overridden</p> Signup and view all the answers

What can abstract classes not do?

<p>be instantiated</p> Signup and view all the answers

You can use a lambda expression to instantiate an object that does what?

<p>implements a functional interface</p> Signup and view all the answers

If a subclass constructor does not explicitly call a superclass constructor, Java will not call any of the superclass's constructors.

<p>False (B)</p> Signup and view all the answers

The superclass constructor always executes before the subclass constructor.

<p>True (A)</p> Signup and view all the answers

When a class contains an abstract method, the class cannot be instantiated.

<p>True (A)</p> Signup and view all the answers

What is the difference between a protected class member and a private class member?

<p>A protected member can be accessed by other classes in the same package. A private member can only be accessed in the class where it is created.</p> Signup and view all the answers

What is the superclass and what is the subclass in the following line? public class Pet extends Dog?

<p>Dog is superclass, Pet is subclass</p> Signup and view all the answers

Can a subclass ever directly access the private members of its superclass?

<p>False (B)</p> Signup and view all the answers

What is the difference between overriding a superclass method and overloading a superclass method?

<p>Overriding means that they have the same signatures in both methods. Overloaded methods have the same name, but different parameter lists.</p> Signup and view all the answers

What is an abstract method?

<p>An abstract method expects to be overridden in the class implementing it.</p> Signup and view all the answers

What is an abstract class?

<p>An abstract class is a class designed with implementation gaps for subclasses to fill in and is deliberately incomplete. It cannot be instantiated.</p> Signup and view all the answers

What is the name of the superclass and the subclass in the following line? public class Truck extends Vehicle?

<p>Vehicle is the superclass, Truck is the subclass</p> Signup and view all the answers

Describe the order in which the class's constructors execute when a class B inherits from class A.

<p>Constructor A first then B.</p> Signup and view all the answers

When you create a class, why does it automatically have a toString method and an equals method?

<p>It receives these methods from the Object class.</p> Signup and view all the answers

How is an interface different from an abstract class, or any class?

<p>Many interfaces can apply to many classes whereas an abstract class can only apply to a subclass.</p> Signup and view all the answers

Write the first line of a class named Employee, which implements an interface named Payable and Listable.

<p>public class Employee implements Payable, Listable</p> Signup and view all the answers

When designing a class hierarchy, what should be true of a superclass?

<p>A superclass should contain the data and functionality that are common to all subclasses that inherit from the superclass.</p> Signup and view all the answers

Study Notes

Inheritance Basics

  • Superclass is the general class in an inheritance relationship.
  • Subclass is the specialized class that extends the functionality of the superclass.
  • The keyword "extends" indicates that a class inherits from another class.

Access Modifiers in Inheritance

  • Subclasses do not have access to private members of the superclass.
  • Protected members of the superclass are accessible to subclasses and classes in the same package.
  • Private members can only be accessed within the class where they are declared.

Class Constructors

  • In a subclass constructor, a call to the superclass constructor must appear as the first statement.
  • The call to the superclass's default constructor can be done using super();.
  • The superclass constructor always executes before the subclass constructor.

Method Overriding and Overloading

  • A method in a subclass that has the same signature as a method in the superclass is an example of overriding.
  • A method in a subclass with the same name but a different signature than a method in the superclass is an example of overloading.
  • Overriding means the same signatures are present in both methods, while overloading has different parameter lists.

Abstract Classes and Methods

  • Abstract methods must be overridden in the subclass implementing them.
  • Abstract classes cannot be instantiated and are intentionally left incomplete for subclasses to fill in the gaps.

Interfaces

  • When a class implements an interface, it must provide implementations for all non-default methods with exact signatures and return types.
  • Fields in an interface are both final and static.
  • An interface allows multiple interfaces to be applied across different classes, unlike abstract classes which relate to a single hierarchy.

Class Declaration and Members

  • Constructors of superclass execute before those of the subclass when a subclass object is created.
  • Class objects implicitly receive methods like toString and equals from the Object class.
  • A subclass can never directly access the private members of its superclass.

Understanding Class Relationships

  • In the declaration public class Pet extends Dog, Dog is the superclass and Pet is the subclass.
  • Abstract classes should encompass common functionality across subclasses, serving as a foundation for derived classes.
  • An Employee class can implement multiple interfaces like Payable and Listable through the syntax public class Employee implements Payable, Listable.

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Enhance your understanding of inheritance in object-oriented programming with these flashcards. Explore key terms such as 'superclass', 'subclass', and 'extends'. Perfect for anyone looking to solidify their knowledge in Chapter 9 of their programming course.

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