Questions and Answers
What is inheritance in Java?
The process where one class acquires the properties (methods and fields) of another.
What is a subclass?
The class which inherits the properties of another (derived class, child class).
What is a superclass?
The class whose properties are inherited (base class, parent class).
What keyword is used to inherit the properties of a class?
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What is the syntax to extend a class?
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What can a superclass reference variable hold?
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What does a subclass inherit from its superclass?
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What is the super keyword used for?
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How do you invoke a superclass constructor?
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What does the IS-A relationship signify?
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How does the extends keyword contribute to inheritance?
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What does the implements keyword do?
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What does the instanceof keyword check?
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What is a HAS-A relationship in Java?
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What are the types of inheritance?
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Study Notes
Inheritance Concepts
- Inheritance enables a class to acquire properties (methods and fields) from another class, structured in a hierarchical manner.
Class Relationships
- Subclass: A derived or child class that inherits properties from another class.
- Superclass: A base or parent class whose properties are inherited by subclasses.
Keywords in Inheritance
- extends: The keyword used to inherit properties from another class.
-
extends Syntax: Defined as
class Sub extends Super { ... }, indicating subclass inherits from superclass.
Superclass Reference
- A reference variable of the superclass can hold subclass objects but provides access only to superclass members. For full access, use a subclass reference variable.
Inheritance Member Access
- Subclasses inherit all members (fields, methods, nested classes) from their superclass, excluding constructors.
- Superclass constructors can be invoked from subclasses using the
superkeyword.
Utilizing the super Keyword
- Distinguishes members of the superclass from subclass members having the same names (e.g.,
super.variable,super.method()). - Calls the superclass constructor, particularly useful for parameterized constructors:
super(values);.
IS-A Relationship
- An IS-A relationship indicates that one object is a type of another.
- Example:
public class Dog extends Mammal, asserting that Dog is a type of Mammal.
Structure of IS-A Relationships
- The
extendskeyword establishes inheritance where subclasses inherit properties of the superclass, excluding private properties. - The
implementskeyword allows classes to inherit properties from interfaces, not from other classes.
instanceof Keyword
- Used to check if an object is an instance of a particular class or interface, confirming relationships within the class hierarchy.
HAS-A Relationship
- Reflects the usage indicating that a certain class possesses or contains another class.
- Enhances code reuse and reduces redundancy by defining classes separately.
Inheritance Types
- Single Inheritance: A subclass inheriting from one superclass.
- Multilevel Inheritance: A class derived from another class, forming a chain of inheritance.
- Hierarchical Inheritance: Multiple subclasses derived from one superclass.
- Multiple Inheritance: A class inheriting from more than one superclass (supported by interfaces in Java).
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Test your knowledge of Java inheritance with these flashcards. Learn key terms like 'inheritance', 'subclass', and 'superclass', and understand how they fit into the object-oriented programming paradigm. Perfect for Java learners looking to reinforce their understanding of class relationships.
