Questions and Answers
A base class is synonymous with a:
A constructor for a derived class begins with an invocation of a constructor for the base class.
True
A derived class contains only public instance variables and public methods from the base class.
False
A derived class is a class defined by adding instance variables and methods to an existing class.
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A derived class is also called a:
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A method or instance variable modified by protected:
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A super class is also called a:
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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.
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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.
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If an instance variable is not modified by public, protected, or private then it is said to have:
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If the final modifier is added to the definition of a method, this means:
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In using the keyword this in place of super(), the invocation of this must be the ________ action taken by the constructor.
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Inheritance is the process by which a new class known as a ________ is created from another class, called the ________.
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Inheritance promotes code:
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Overriding is when a derived class redefines a method from the base class.
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Private methods of the base class are not available for use by derived classes.
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The Object class contains the method:
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The call to the base class constructor (super) must always be the last action taken in a constructor definition.
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The class ________ is an ancestor class of all Java classes.
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The equals method for a class should have ________ as the type of its one parameter.
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The keyword extends indicates:
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The special syntax for invoking a constructor of the base class is:
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What does a derived class automatically inherit from the base class?
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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.
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You may substitute the keyword this for super() to call a constructor of...
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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
thismust be the first action taken by the constructor when substituting forsuper().
Object Class and Methods
- The Object class serves as the ancestor for all Java classes, providing fundamental methods such as
getClass(),toString(), andequals(). - 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
extendskeyword 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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Description
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!
