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Questions and Answers
What is the primary purpose of abstraction?
What is the primary purpose of abstraction?
Which of the following is a characteristic of inner classes?
Which of the following is a characteristic of inner classes?
What is the term for creating objects from other objects?
What is the term for creating objects from other objects?
What is the term for converting a superclass to its subclass?
What is the term for converting a superclass to its subclass?
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Which of the following is an example of abstraction?
Which of the following is an example of abstraction?
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What is the purpose of encapsulation?
What is the purpose of encapsulation?
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What is the purpose of inheritance in object-oriented programming?
What is the purpose of inheritance in object-oriented programming?
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What is the term for when multiple methods with the same name can be defined with different parameter lists?
What is the term for when multiple methods with the same name can be defined with different parameter lists?
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What is the primary goal of encapsulation in object-oriented programming?
What is the primary goal of encapsulation in object-oriented programming?
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What is the purpose of an interface in object-oriented programming?
What is the purpose of an interface in object-oriented programming?
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What is the term for when a subclass provides a specific implementation for a method that is already defined in its superclass?
What is the term for when a subclass provides a specific implementation for a method that is already defined in its superclass?
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What is the primary benefit of encapsulation in object-oriented programming?
What is the primary benefit of encapsulation in object-oriented programming?
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What is the term for showing only the necessary information to the outside world while hiding the implementation details?
What is the term for showing only the necessary information to the outside world while hiding the implementation details?
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What is the keyword used to implement inheritance in Java?
What is the keyword used to implement inheritance in Java?
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Study Notes
Inheritance
- Inheritance is a mechanism in which one class can inherit the properties and behavior of another class.
- The class that is being inherited from is called the superclass or parent class.
- The class that is doing the inheriting is called the subclass or child class.
- Inheritance is implemented using the
extendskeyword. - A subclass inherits all the fields and methods of its superclass.
- A subclass can also override the methods of its superclass.
Polymorphism
- Polymorphism is the ability of an object to take on multiple forms.
- There are two types of polymorphism:
- Method Overloading: When multiple methods with the same name can be defined with different parameter lists.
- Method Overriding: When a subclass provides a specific implementation for a method that is already defined in its superclass.
- Polymorphism is achieved through method overriding and method overloading.
Encapsulation
- Encapsulation is the concept of bundling data and methods that operate on that data within a single unit.
- In Java, encapsulation is achieved through the use of classes and objects.
- Data is hidden from the outside world and can only be accessed through methods provided by the class.
- Encapsulation helps to:
- Hide implementation details
- Improve data security
- Reduce coupling between objects
Interfaces
- An interface is a abstract class that defines a contract that must be implemented by any class that implements it.
- An interface defines a set of methods that must be implemented by any class that implements it.
- Interfaces are abstract and cannot be instantiated.
- Interfaces are used to define a common set of methods that can be called by other classes.
- Interfaces are implemented using the
implementskeyword.
Abstraction
- Abstraction is the concept of showing only the necessary information to the outside world while hiding the implementation details.
- Abstraction helps to:
- Reduce complexity
- Improve modularity
- Improve code reusability
- Abstraction is achieved through abstract classes and interfaces.
Inner Classes
- An inner class is a class that is defined inside another class.
- Inner classes have access to the members of the outer class.
- Inner classes can be used to implement helper classes or to encapsulate data and behavior.
- Inner classes can be static or non-static.
Composition
- Composition is the concept of creating objects from other objects.
- Composition is a "has-a" relationship between objects.
- Composition is used to create complex objects from simpler objects.
- Composition is achieved through the use of containers and component objects.
Downcasting and Upcasting
- Casting is the process of converting one object type to another.
- There are two types of casting:
- Upcasting: Converting a subclass to its superclass.
- Downcasting: Converting a superclass to its subclass.
- Upcasting is implicit and can be done without an explicit cast.
- Downcasting is explicit and requires an explicit cast.
- Downcasting can result in a
ClassCastExceptionif the object is not of the correct type.
Inheritance
- A class can inherit properties and behavior of another class using the
extendskeyword. - The inherited class is called the subclass or child class, while the class being inherited from is called the superclass or parent class.
- A subclass inherits all fields and methods of its superclass and can also override them.
Polymorphism
- Polymorphism is the ability of an object to take on multiple forms.
- There are two types of polymorphism: Method Overloading (multiple methods with the same name but different parameter lists) and Method Overriding (subclass provides a specific implementation for a method already defined in its superclass).
- Polymorphism is achieved through method overriding and method overloading.
Encapsulation
- Encapsulation is the concept of bundling data and methods that operate on that data within a single unit.
- In Java, encapsulation is achieved through the use of classes and objects.
- Data is hidden from the outside world and can only be accessed through methods provided by the class.
- Encapsulation helps to hide implementation details, improve data security, and reduce coupling between objects.
Interfaces
- An interface is an abstract class that defines a contract that must be implemented by any class that implements it.
- An interface defines a set of methods that must be implemented by any class that implements it.
- Interfaces are abstract and cannot be instantiated.
- Interfaces are used to define a common set of methods that can be called by other classes and are implemented using the
implementskeyword.
Abstraction
- Abstraction is the concept of showing only the necessary information to the outside world while hiding the implementation details.
- Abstraction helps to reduce complexity, improve modularity, and improve code reusability.
- Abstraction is achieved through abstract classes and interfaces.
Inner Classes
- An inner class is a class that is defined inside another class.
- Inner classes have access to the members of the outer class.
- Inner classes can be used to implement helper classes or to encapsulate data and behavior.
- Inner classes can be static or non-static.
Composition
- Composition is the concept of creating objects from other objects.
- Composition is a "has-a" relationship between objects.
- Composition is used to create complex objects from simpler objects and is achieved through the use of containers and component objects.
Downcasting and Upcasting
- Casting is the process of converting one object type to another.
- There are two types of casting: Upcasting (converting a subclass to its superclass) and Downcasting (converting a superclass to its subclass).
- Upcasting is implicit and can be done without an explicit cast.
- Downcasting is explicit and requires an explicit cast, and can result in a
ClassCastExceptionif the object is not of the correct type.
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Description
Understand the basics of object-oriented programming in Java, including inheritance and polymorphism.
