Java Chapter 7 Flashcards
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Questions and Answers

A base class is synonymous with a:

  • Derived class (correct)
  • Sub class
  • Parent class (correct)
  • Child class

    • A constructor for a derived class begins with an invocation of a constructor for the base class.

    True (A)

    A derived class contains only public instance variables and public methods from the base class.

    False (B)

    A derived class is a class defined by adding instance variables and methods to an existing class.

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

    A derived class is also called a:

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

    A method or instance variable modified by protected:

    <p>Cannot be accessed by name in any other class (that is, other than classes named in A-C.) (D)</p> Signup and view all the answers

    A super class is also called a:

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

    An instance variable (or method) that is private in a base class is accessible by name in the definition of a method in any other class.

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

    An object of a derived class has the type of the derived class, and it also has the type of the base class, and more generally, has the type of every one of its ________ classes.

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

    If an instance variable is not modified by public, protected, or private then it is said to have:

    <p>All of these (C)</p> Signup and view all the answers

    If the final modifier is added to the definition of a method, this means:

    <p>The method may not be redefined in the derived class. (C)</p> Signup and view all the answers

    In using the keyword this in place of super(), the invocation of this must be the ________ action taken by the constructor.

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

    Inheritance is the process by which a new class known as a ________ is created from another class, called the ________.

    <p>base class = inherited class derived class = base class inherited class = base class</p> Signup and view all the answers

    Inheritance promotes code:

    <p>Reuse (C)</p> Signup and view all the answers

    Overriding is when a derived class redefines a method from the base class.

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

    Private methods of the base class are not available for use by derived classes.

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

    The Object class contains the method:

    <p>All of these (C)</p> Signup and view all the answers

    The call to the base class constructor (super) must always be the last action taken in a constructor definition.

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

    The class ________ is an ancestor class of all Java classes.

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

    The equals method for a class should have ________ as the type of its one parameter.

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

    The keyword extends indicates:

    <p>Inheritance (C)</p> Signup and view all the answers

    The special syntax for invoking a constructor of the base class is:

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

    What does a derived class automatically inherit from the base class?

    <p>All of these (C)</p> Signup and view all the answers

    When you define a derived class, you give only the added instance variables and the added methods as well as all the methods from the base class.

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

    You may substitute the keyword this for super() to call a constructor of...

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

    Study Notes

    Class Hierarchy and Inheritance

    • Parent class refers to a base class from which other classes can derive.
    • A derived class is synonymous with a subclass, indicating the relationship in inheritance.
    • A constructor in a derived class begins by invoking the constructor of the base class, ensuring proper initialization.

    Access Modifiers and Visibility

    • The private instance variables or methods in a base class are not accessible in any derived class.
    • Protected variables can only be accessed by derived classes and classes in the same package, limiting visibility.
    • If an instance variable is not specified as public, protected, or private, it has default access (package access).

    Final Keyword

    • If a method is marked with the final modifier, it cannot be redefined in any derived class, ensuring its integrity.
    • The invocation of this must be the first action taken by the constructor when substituting for super().

    Object Class and Methods

    • The Object class serves as the ancestor for all Java classes, providing fundamental methods such as getClass(), toString(), and equals().
    • The equals method should take an Object parameter to ensure compatibility with all Java object types.

    Inheritance Mechanism

    • Inheritance allows a new class (derived class) to be created from an existing class (base class), promoting code reuse.
    • Derived classes inherit instance variables, static variables, and public methods from their base class.
    • Overriding occurs when a derived class redefines a method from its base class.

    Inheritance Keywords

    • The extends keyword indicates inheritance in Java, specifying the relationship between base and derived classes.
    • The special keyword super() is used to call the constructor of the base class within a derived class.

    Truth Statements

    • A derived class is defined by adding instance variables and methods to an existing class.
    • Private methods from the base class cannot be accessed by the derived class, maintaining encapsulation.
    • The call to the base class constructor (super) does not need to be the last action in a constructor.

    General Concepts

    • Instantiation of a derived class results in an object that holds the type of the derived class and its base class, extending to all ancestor types.
    • Code reuse through inheritance reduces redundancy and promotes better organization of code in Java.

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    Test your knowledge of key concepts from Java Chapter 7 with these flashcards. Explore important terms like parent class, constructors, and the relationship between derived and base classes. Perfect for reinforcing your understanding of object-oriented programming in Java!

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