What Do You Know About C++ Polymorphism? Trivia Quiz

Polymorphism allows objects of different classes that are connected through a class hierarchy to be treated uniformly. This means that even though these objects have different types, they can be processed in a generic manner using a common interface or superclass. This flexibility in handling different objects simplifies code and promotes reusability. Therefore, the statement is true.

Polymorphism is a concept in object-oriented programming that allows objects of different classes to be treated as objects of a common superclass. This means that even if you do not know the specific type of an object, you can still perform operations on it using methods defined in the superclass. This flexibility enables you to write code that can work with a wide variety of objects, making it easier to create reusable and adaptable code. Therefore, the statement that polymorphism allows you to command a wide variety of objects even if you do not know their types is true.

Sealing methods in programming refers to the practice of marking a class or method as "final" to prevent it from being overridden or extended by other classes. By sealing a method, the compiler can determine at compile-time that the method will not be overridden, allowing it to optimize the program by inlining the code. This means that the compiler can replace the method call with the actual code of the method, eliminating the overhead of a function call. Therefore, the statement "Sealing methods allows the compiler to optimize the program by 'inlining code'" is true.

An abstract base class can be used to declare references because it provides a common interface for its derived classes. This allows objects of different derived classes to be referenced using a pointer or reference of the abstract base class type. By declaring a reference to the abstract base class, we can access the common functionality defined in the base class, while still being able to use specific functionality implemented in the derived classes. This helps in achieving polymorphism and code reusability.

Abstract methods and properties in a class are declared without any implementation. They serve as placeholders for methods and properties that must be implemented in any class that inherits from the abstract class. This allows the abstract class to define a common interface that all its subclasses must adhere to, while leaving the specific implementation details to the subclasses. Therefore, the statement that abstract methods and properties do not provide an implementation is true.

An abstract class can indeed be derived from another abstract class. This is because abstract classes are designed to be extended and serve as a base for other classes. By deriving one abstract class from another, we can further define and specialize the behavior and attributes of the derived class while still maintaining the abstract nature of the base class. This allows for a hierarchical structure in the design of classes, where each level of abstraction adds more specific functionality.

When a method needs to be called polymorphically, it means that the method can be overridden by a subclass. In order to achieve this, a reference of the base class that defines the behavior of the object should be used to point to the object. This allows the method to be called based on the actual type of the object at runtime, rather than the type of the reference. By using a reference of the base class, we ensure that the correct version of the method is called, even if the object is of a subclass type.

Both B and C are correct statements. Polymorphism is indicated by the use of the keyword virtual in a method signature, which allows a derived class to override the implementation of the base class method. Polymorphism is also indicated by the use of the keyword override in a method signature, which explicitly states that the method is intended to override a base class method. These keywords enable the flexibility and extensibility of object-oriented programming, allowing for dynamic method dispatch and the ability to treat objects of different classes as instances of a common base class.

The keyword sealed is used to prevent overriding and inheritance in methods and classes. By applying the sealed keyword, we ensure that a method or class cannot be overridden by any derived class, and it cannot be inherited by any other class. This helps in maintaining the integrity and stability of the code, as it prevents unintended modifications or extensions of the sealed elements.

When a derived class reference is assigned to a base class variable, the base class variable only has access to the methods and properties of the base class. In order to call any methods specific to the derived class, the base class variable must be cast back to the derived class. This allows the variable to regain its original derived class type and access the additional methods and properties that are specific to the derived class. Therefore, the statement is true.

The correct answer is "All of the above." Any concrete subclass that extends class Foo must implement a method called calculate. Additionally, the instance variable "a" is private, meaning it cannot be accessed by subclasses. Lastly, since Foo is an abstract class, it cannot be instantiated directly. Therefore, all of the given statements are true.

Polymorphism allows for specifics to be dealt with during execution. This means that the behavior of an object can be determined at runtime based on its specific type. During execution, the appropriate method or implementation will be chosen based on the actual type of the object, allowing for flexibility and dynamic behavior. Polymorphism is a key feature in object-oriented programming languages that enables code reusability and flexibility.

Polymorphism allows the creation of programs that can work with different classes in a general manner. It enables the use of a single interface to represent multiple classes, allowing objects of different classes to be treated uniformly. This flexibility is particularly useful when dealing with different types of objects that share common behavior or attributes. It simplifies code implementation and maintenance, as it allows for code reuse and promotes modularity. Therefore, the correct answer is that polymorphism enables the handling of a wide variety of classes in a general manner.

When a method is declared as sealed, it means that it cannot be overridden by any derived class. This is useful in situations where the base class wants to prevent any modifications or extensions to a particular method implementation. By sealing the method, the base class ensures that it retains control over the behavior of the method and prevents any changes that could potentially break its functionality. This helps in maintaining the integrity and consistency of the code.

Polymorphism enables you to program in the general by allowing you to write code that can work with objects of different classes, as long as they share a common interface or superclass. This means that you can write code that is more flexible and reusable, as it can handle different types of objects without needing to know their specific implementation details.

False. Parts of a program that need modification are those that require direct knowledge of the particular class that's added to the hierarchy.

An interface in programming is a way to define a contract or a set of rules that a class must follow. It allows different types of objects to have the same functionality, even though each object may implement that functionality differently. This means that objects of different classes can be treated interchangeably as long as they adhere to the interface. Therefore, the purpose of an interface is to provide different types of objects with comparable functionality, regardless of how they implement it.

Assigning a derived class reference to a base class variable is safe because the derived class is an object of its base class. This means that the derived class inherits all the properties and behaviors of the base class. Therefore, assigning a derived class reference to a base class variable allows us to access the base class's members through the derived class reference, ensuring that no data or functionality is lost in the process.

False. Polymorphism can be used to include classes that were not even envisioned during program development.

A derived class reference can be assigned to a base class variable because a derived class is a specialization of the base class and contains all the properties and methods of the base class. However, a base class reference cannot be assigned to a derived class variable because a base class does not have all the properties and methods of the derived class. The derived class may have additional features that are not present in the base class.

False. This is a compilation error.

An interface is best used for providing services that bring together objects of otherwise unrelated classes. This is because an interface allows classes to define a set of methods that they must implement, regardless of their class hierarchy. By implementing the same interface, objects of different classes can be treated uniformly and interact with each other through the common interface methods. This promotes loose coupling and flexibility in the design, allowing for greater reusability and extensibility of code.

The correct answer is "public abstract int method1();". This declaration correctly declares an abstract method named method1 in an abstract class named Class1. The method is declared with a return type of int and takes no arguments. The keywords "public" and "abstract" are used to specify the access level and the abstract nature of the method, respectively.

False. Attempting to provide an implementation for an abstract method is a syntax error.

Sealed methods are not necessarily static. The purpose of declaring a method as sealed is to prevent further inheritance and overriding of that method in derived classes. Sealed methods can still be instance methods and can be called on objects of the class. On the other hand, static methods belong to the class itself and can be called without creating an instance of the class. Therefore, the statement that sealed methods are static is incorrect.