Scientific Programming Chapter 9 Flashcards

Questions and Answers

What does the keyword 'extends' indicate?

A class is declared final

A superclass has multiple subclasses

A class implements an interface

A subclass will inherit from a superclass (correct)

What is the Object class in Java?

The superclass of all Java classes (correct)

A class with no methods

The first class that is declared in a program

A class that cannot be inherited

What is class hierarchy?

A set of classes related by inheritance.

What does 'protected' mean in terms of access modifiers?

Protected members can be accessed in the class in which they are defined and in all subclasses of that class. Signup and view all the answers

What is inheritance in object-oriented programming?

An is-a relationship. Signup and view all the answers

What does the 'super' keyword do?

It refers to an object's superclass members. Signup and view all the answers

Define direct superclass.

A subclass's immediate superclass. Signup and view all the answers

What is meant by 'brittle software'?

A small change in the superclass can break subclass implementations. Signup and view all the answers

What does it mean to override a method?

To define a subclass method with the same signature as a superclass method. Signup and view all the answers

What is a clone method?

A protected method that takes no arguments and returns a copy of the object on which it is called. Signup and view all the answers

Define indirect superclass.

A class that a subclass does not directly extend but still has an is-a relationship with the class. Signup and view all the answers

A subclass can explicitly invoke a constructor of its superclass by using the superclass constructor call syntax-keyword ______ followed by a set of parentheses containing the superclass constructor's arguments.

super Signup and view all the answers

Every object of a ___ is also an object of that class's _. However, a _ object is not an object of any of its ___.

subclass, superclass, superclass, subclasses Signup and view all the answers

In a(n) _____ relationship, an object has a reference to an object of another class as a member.

has-a Signup and view all the answers

In a(n) _____ relationship, an object of a subclass type may also be treated as an object of the superclass type.

is-a Signup and view all the answers

What are standardized reusable components?

Components that new software is likely to be constructed from. Signup and view all the answers

What does private mean in terms of member access?

A subclass cannot directly access private members of its superclass. Signup and view all the answers

What is the direct superclass of a subclass?

The superclass from which the subclass inherits. Signup and view all the answers

With _ inheritance, a class is derived from one superclass. Java does not support _ inheritance.

single Signup and view all the answers

A subclass inherits the members of its superclass that are declared with the access specifiers _ and _

public, protected Signup and view all the answers

Which class normally overrides the toString method?

Object class Signup and view all the answers

How does inheritance promote software reusability?

Inheritance enables programmers to create new classes from existing classes by absorbing their attributes and behaviors. Signup and view all the answers

Explain protected member access.

Protected members are accessible to the defining class, all subclasses, and other classes in the same package. Signup and view all the answers

Explain the difference between composition and inheritance.

With inheritance, a class inherits attributes and behaviors from another class. With composition, a class is composed of objects of existing classes. Signup and view all the answers

Explain the initialization process for an object of class BasePlusCommissionEmployee.

The BasePlusCommissionEmployee constructor is called, which calls CommissionEmployee's constructor, which then calls Object's constructor. Signup and view all the answers

How to invoke a superclass method from a subclass method?

Use the keyword super to invoke the superclass method if the subclass method overrides it; otherwise, use the name of the superclass method. Signup and view all the answers

Study Notes

Java Inheritance Concepts

Inheritance allows a subclass to inherit properties and methods from a superclass, creating a hierarchical relationship.
The Object class serves as the ultimate superclass for all Java classes.
Class relationships established through inheritance are termed class hierarchy.

Access Modifiers

Protected members can be accessed within the defining class and all its subclasses, as well as other classes in the same package.
Private members remain inaccessible to subclasses, ensuring encapsulation.
Members declared with public and protected access specifiers are inherited by subclasses.

Keywords in Inheritance

The extends keyword indicates that a subclass inherits from a particular superclass.
The super keyword is used to refer to superclass members and to call a superclass constructor.
When a subclass invokes a constructor of its superclass, it does so with the super keyword followed by the appropriate parameters.

Types of Relationships

Is-a relationship indicates that a subclass is a specialized type of a superclass.
Has-a relationship signifies that an object includes a reference to another object as a member.
Inheritance leads to brittle software, where minor changes in superclasses can disrupt subclass functionality.

Method Overriding and Cloning

Method override occurs when a subclass defines a method with the same signature as a method in its superclass.
The clone method is a protected method that creates a copy of the object it is called on.

Composition vs. Inheritance

Inheritance grants a new class attributes and behaviors from an existing one, allowing for dual treatment as its type and superclass types.
Composition involves creating a new class from existing classes’ instances, where the new class typically cannot be treated as an instance of the component classes.

Object Initialization

When creating an object of a derived class, constructors from the superclass are invoked in sequence, starting from the highest ancestor.
In the BasePlusCommissionEmployee example, constructors are called in a chain from Object to CommissionEmployee, finally reaching BasePlusCommissionEmployee, which initializes additional attributes.

Accessing Superclass Methods

To invoke a superclass method from an overriding subclass method, use the super keyword.
If the subclass method does not override the superclass one, simply call the superclass method by its name with the necessary arguments.

Software Design Principles

Standardized reusable components are a future trend in software construction, paralleling manufacturing practices in industries like automotive.

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Test your understanding of key concepts from Chapter 9 of Scientific Programming. This quiz covers essential terminology relating to class inheritance, object classes, and access modifiers in Java. Flashcards are a great way to reinforce your learning and prepare for exams.