OOP Concepts and UML
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Questions and Answers

Which keyword is used to declare a class as abstract?

  • final
  • abstract (correct)
  • public
  • static

    • Can an abstract class have any objects created from it?

  • Yes, by using the 'new' operator
  • No, abstract classes cannot have objects created from them (correct)
  • Yes, but only if the abstract class has at least one abstract method
  • Yes, but only if the abstract class is fully defined

    • Is it necessary for a derived class to implement all the abstract methods of the base class?

  • Only if the derived class is also declared as abstract
  • No, the derived class can choose which abstract methods to implement
  • Yes, it is necessary for the derived class to implement all abstract methods (correct)
  • No, abstract methods are optional for the derived class

    • Which one of the following is true about default methods in Java interfaces?

    <p>Default methods can be used to define optional methods in an interface.</p> Signup and view all the answers

    What is the strongest relationship that can exist among the Bank, Account, and Customer classes in a Java program?

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

    Which class extends the Bank class and overrides its getRateOfInterest() method?

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

    Which classes should implement the Account interface in a Java banking system program?

    <p>Bank, Account, and CurrentAccount</p> Signup and view all the answers

    Which one of the following statements is true about dependency in object-oriented programming?

    <p>A class has some sort of dependency on another class</p> Signup and view all the answers

    What does the «creates» stereotype indicate in an association relationship?

    <p>The source of the association creates the target</p> Signup and view all the answers

    What is the difference between aggregation and composition in object-oriented programming?

    <p>Aggregation indicates a part of a whole relationship, while composition indicates a whole to its parts relationship</p> Signup and view all the answers

    What is the purpose of extending an interface in object-oriented programming?

    <p>To inherit the methods and variables of another interface</p> Signup and view all the answers

    Which keyword is used to declare a class as final in Java?

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

    Which of the following is NOT a characteristic of interfaces in Java?

    <p>Interfaces can have instance variables</p> Signup and view all the answers

    What is the purpose of the 'implements' keyword in Java?

    <p>To indicate that a class implements an interface</p> Signup and view all the answers

    What is the correct syntax to implement multiple interfaces in Java?

    <p>class MyClass implements Interface1, Interface2</p> Signup and view all the answers

    Which keyword is used to declare a class as abstract in Java?

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

    Can an abstract class have constructors?

    <p>Yes, an abstract class can have constructors.</p> Signup and view all the answers

    What is the purpose of an abstract method in a superclass?

    <p>To force subclasses to provide their own implementation of the method.</p> Signup and view all the answers

    Which of the following statements is true about default methods in Java interfaces?

    <p>Default methods can be overridden by implementing classes.</p> Signup and view all the answers

    What is the purpose of extending an interface in object-oriented programming?

    <p>To add additional methods to the extended interface.</p> Signup and view all the answers

    What is the difference between aggregation and composition in object-oriented programming?

    <p>Aggregation implies a whole-part relationship, while composition implies a has-a relationship.</p> Signup and view all the answers

    What is the correct syntax to implement multiple interfaces in Java?

    <p>class MyClass implements Interface1, Interface2 { }</p> Signup and view all the answers

    Which one of the following statements is true about the relationship between aggregation and composition in object-oriented programming?

    <p>Composition is a stronger relationship than aggregation.</p> Signup and view all the answers

    Which one of the following statements is true about inheritance in object-oriented programming?

    <p>Inheritance allows a class to inherit methods and fields from only one parent class.</p> Signup and view all the answers

    Which one of the following statements is true about interfaces in Java?

    <p>An interface can implement another interface.</p> Signup and view all the answers

    Which one of the following statements is true about the 'extends' and 'implements' keywords in Java?

    <p>An interface can use 'extends' to inherit from multiple interfaces.</p> Signup and view all the answers

    Which one of the following statements is true about final methods in Java?

    <p>Final methods cannot be overridden by subclasses.</p> Signup and view all the answers

    What is the purpose of interfaces in Java?

    <p>Interfaces allow you to fully abstract a class.</p> Signup and view all the answers

    Which of the following is true about default methods in Java interfaces?

    <p>Default methods have a body and can be overridden by implementing classes.</p> Signup and view all the answers

    What is the purpose of the 'implements' keyword in Java?

    <p>The 'implements' keyword is used to indicate that a class is implementing an interface.</p> Signup and view all the answers

    Study Notes

    Abstract Classes

    • The keyword abstract is used to declare a class as abstract.
    • An abstract class cannot have objects created from it.
    • It is not necessary for a derived class to implement all the abstract methods of the base class.

    Interfaces

    • Default methods in Java interfaces allow adding new functionality to an interface without breaking the implementing classes.
    • An interface can be extended by another interface.
    • Multiple interfaces can be implemented by a class using the implements keyword, separated by commas.

    Class Relationships

    • The strongest relationship that can exist among the Bank, Account, and Customer classes in a Java program is composition.
    • A derived class can extend the Bank class and override its getRateOfInterest() method.
    • The classes that should implement the Account interface in a Java banking system program are those that represent types of accounts.

    Object-Oriented Programming

    • Dependency in object-oriented programming is a relationship where one class uses another class.
    • The «creates» stereotype indicates a creation relationship in an association relationship.
    • Aggregation is a relationship where one class contains a collection of another class, while composition is a relationship where one class owns a collection of another class.
    • The purpose of extending an interface is to add new functionality or to create a new interface that is a modified version of the original interface.

    Keywords

    • The keyword final is used to declare a class as final in Java.
    • Interfaces in Java cannot have instances created from them, and all methods are abstract.
    • The implements keyword is used to implement one or more interfaces in a class.
    • The correct syntax to implement multiple interfaces in Java is class MyClass implements Interface1, Interface2, ....
    • The keyword abstract is used to declare a class as abstract in Java.
    • Abstract classes can have constructors.

    Methods

    • The purpose of an abstract method in a superclass is to provide a blueprint for a method that must be implemented by its subclasses.
    • Default methods in Java interfaces allow adding new functionality to an interface without breaking the implementing classes.
    • Final methods in Java cannot be overridden by subclasses.

    Inheritance

    • Inheritance in object-oriented programming is a mechanism of creating a new class from an existing class.

    Interfaces

    • The purpose of interfaces in Java is to define a contract that must be implemented by any class that implements it.

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    Description

    Test your knowledge on class relationships and associations with this quiz. Learn about dependencies and associations between classes, including examples and definitions. Perfect for anyone studying object-oriented programming.

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