Polymorphism and Interfaces: Master Object-Oriented Programming Concepts

Question 1

Which of the following is NOT a valid approach for achieving polymorphism in Java?

Accepted Answer

Constructor Overloading

Answer

Method Overloading

Answer

Method Overriding

Answer

Interface Implementation

Question 2

When implementing an interface in Java, which requirement must be fulfilled?

Accepted Answer

Implement all methods declared in the interface

Answer

Extend the interface class

Answer

Override the default method implementations

Answer

Compile the interface together with the implementing class

Question 3

Describe the primary purpose of the @Override annotation in Java.

Accepted Answer

To indicate that a method is overriding a method from a superclass.

Answer

To prevent a method from being overridden by subclasses.

Answer

To designate a method as abstract.

Answer

To specify the return type of a method.

Question 4

What is a potential disadvantage of polymorphism in object-oriented programming?

Accepted Answer

Increased complexity

Answer

Code reusability

Answer

Improved code performance

Question 5

In practical software development, which forms of polymorphism are most commonly employed?

Accepted Answer

Method overriding and overloading

Answer

Covariance and contravariance

Answer

Subtype polymorphism and parametric polymorphism

Question 6

Which of the following is NOT a benefit of using polymorphism in OOP?

Accepted Answer

Reduced code complexity

Answer

Code reusability

Answer

Improved code maintainability

Answer

Flexibility in code design

Question 7

In inheritance, what is the relationship between a superclass and a subclass?

Accepted Answer

The subclass inherits properties and methods from the superclass

Answer

The superclass inherits properties and methods from the subclass

Answer

They have no relationship

Answer

They are completely separate classes

Question 8

Which of the following is a key aspect of interfaces in OOP?

Accepted Answer

They define contracts that classes must implement

Answer

They enable multiple inheritance

Answer

They provide a mechanism for dynamic method binding

Answer

They allow for method overloading

Question 9

Differentiate between method overriding and method overloading.

Accepted Answer

Method overriding changes the implementation of an inherited method, while overloading creates new methods with different parameters

Answer

Method overloading changes the implementation of an inherited method, while overriding creates new methods with different parameters

Answer

Both change the behavior of existing methods

Answer

There is no difference between them

Question 10

Write a valid Java interface declaration.

Accepted Answer

public interface MyInterface {}

Answer

protected interface MyInterface {}

Answer

final interface MyInterface {}

Answer

private interface MyInterface {}

Question 11

What is the function of the 'throws' keyword in Java methods?

Accepted Answer

To indicate the possibility of an exception being thrown

Answer

To handle exceptions that may occur in the method

Answer

To catch exceptions that are thrown by the method

Answer

To prevent the method from throwing exceptions

Question 12

Which of these is NOT a type of exception in Java?

Accepted Answer

Compile-time exception

Answer

Checked exception

Answer

Unchecked exception

Answer

Custom exception

Question 13

What is the purpose of using a finally block in Java?

Accepted Answer

To execute code regardless of whether an exception occurs

Answer

To catch exceptions that are thrown by the method

Answer

To prevent the method from throwing exceptions

Answer

To handle exceptions that are caught by the method

Question 14

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

Accepted Answer

To ensure shared data is always visible and up-to-date across threads

Answer

To prevent a variable from being modified by multiple threads

Answer

To synchronize access to a variable

Answer

To atomically update the value of a variable

Question 15

Which of the following is a potential limitation of using polymorphism in object-oriented programming?

Accepted Answer

Unexpected behavior and maintenance challenges

Answer

Enhanced code readability

Answer

Improved code maintainability

Question 16

What is the primary purpose of an interface in Java?

Accepted Answer

To define a contract that must be implemented by any class that implements it

Answer

To create a new data type

Answer

To provide access to private members of a class

Answer

To inherit methods from another class

Question 17

Which of the following best describes the concept of method overriding?

Accepted Answer

Redefining a method in a subclass with the same name and signature as a method in a superclass

Answer

Implementing a method in a class that implements an interface

Answer

Calling a method through a polymorphic reference

Answer

Using a superclass reference to access a method in a subclass

Question 18

Which of the following is NOT a benefit of polymorphism?

Accepted Answer

Increased code complexity

Answer

Code reusability and extensibility

Answer

Reduced coupling

Answer

Increased maintainability

Question 19

Which of the following is the correct syntax to declare an interface in Java?

Accepted Answer

interface InterfaceName { }

Answer

class InterfaceName { }

Answer

abstract class InterfaceName { }

Answer

enum InterfaceName { }

Question 20

Which of the following is a valid way to implement an interface in Java?

Accepted Answer

Using the 'implements' keyword

Answer

Using the 'extends' keyword

Answer

Using the 'derived from' keyword

Answer

Using the 'inherits' keyword

Question 21

Which of the following is a difference between method overriding and method overloading?

Accepted Answer

Overriding changes the implementation of an inherited method, while overloading creates new methods with the same name but different parameters.

Answer

Overloading changes the implementation of an inherited method, while overriding creates new methods with the same name but different parameters.

Answer

Overriding and overloading both change the implementation of existing methods.

Answer

Overriding and overloading both create new methods with different names and parameters.

Question 22

Which of the following is NOT a type of polymorphism?

Accepted Answer

Type casting

Answer

Overloading

Answer

Overriding

Answer

Parametric polymorphism

Question 23

Which of the following best describes a primary benefit of polymorphism in object-oriented programming?

Accepted Answer

Enhanced code flexibility through method overriding

Answer

Improved code readability

Answer

Increased code efficiency

Answer

Reduced code complexity

Question 24

In Java, what is the primary function of an interface?

Accepted Answer

To define a blueprint for implementing specific behaviors in classes

Answer

To provide a way to group related classes together

Answer

To enhance code security

Answer

To facilitate code inheritance

Question 25

What is the primary distinction between an abstract class and an interface in Java?

Accepted Answer

Abstract classes can have implemented methods, while interfaces cannot

Answer

Interfaces can be instantiated, while abstract classes cannot

Answer

Abstract classes cannot inherit from other classes, while interfaces can

Answer

Interfaces can have constructors, while abstract classes cannot

Question 26

Which of the following is NOT a characteristic associated with polymorphism?

Accepted Answer

It enhances code rigidity

Answer

It enables objects of different classes to respond to the same message

Answer

It reduces code duplication

Answer

It increases code flexibility

Question 27

Consider the following Java code: 
interface Drawable { void draw(); } 
class Circle implements Drawable { ... } 
Which statement accurately reflects the relationship between Circle and Drawable?

Accepted Answer

Circle can be used in any context where Drawable is expected

Answer

Drawable can be used in any context where Circle is expected

Answer

Circle and Drawable are unrelated

Answer

The code will not compile successfully

Question 28

Which of the following is NOT considered an advantage of utilizing interfaces in object-oriented programming?

Accepted Answer

Increased code redundancy

Answer

Improved separation of concerns

Answer

Increased code extensibility

Answer

Reduced code complexity

Question 29

In Java, what is the primary purpose of the "extends" keyword?

Accepted Answer

To define a subclass

Answer

To establish a new interface

Answer

To implement an interface

Answer

To create an abstract class

Question 30

Which of the following correctly describes the usage of the "implements" keyword in Java?

Accepted Answer

To indicate that a class implements a specified interface

Answer

To define a new interface

Answer

To establish a subclass

Answer

To implement an abstract method

Question 31

How do polymorphism and inheritance collaborate to enhance code reusability in object-oriented programming?

Accepted Answer

Polymorphism allows subclasses to inherit and customize methods from their superclass, promoting code reuse.

Answer

Interfaces define a contract for classes to implement, ensuring consistency but not directly supporting polymorphism.

Answer

Inheritance alone achieves code reuse by enabling classes to inherit methods from a common base class.

Answer

Polymorphism and interfaces are separate concepts in object-oriented programming.

Question 32

In object-oriented programming, polymorphism allows objects to share a common interface. Which of the following best describes polymorphism and its types?

Accepted Answer

Polymorphism enables objects from different classes to share a common interface, allowing method overriding based on the object's actual class at runtime, facilitating code reusability and flexibility.

Answer

Polymorphism restricts objects to having similar names but different implementations, preventing code reuse and hindering flexibility in object-oriented programming.

Answer

Polymorphism is solely achieved through class inheritance and cannot be applied dynamically during program execution.

Answer

Polymorphism allows objects to inherit from multiple parent classes, enabling the combination of different functionalities into a single object.

Question 33

In Java, which keyword is used exclusively to define an interface?

Accepted Answer

interface

Answer

abstract

Answer

class

Answer

extend

Question 34

Which of the following accurately describes how to implement an interface in a Java class?

Accepted Answer

Use the 'implements' keyword in the class declaration.

Answer

Inherit from the interface using the 'extends' keyword.

Answer

Assign the interface type to the class.

Answer

Override all methods declared in the interface.

Question 35

What is a fundamental difference between method overriding and method overloading?

Accepted Answer

Method overriding alters an existing method's behavior, while method overloading introduces new methods with distinct signatures.

Answer

Method overriding is used for inheritance while method overloading is used for polymorphism.

Question 36

What is the primary purpose of the 'super' keyword in the context of Java polymorphism?

Accepted Answer

To access and invoke overridden methods from the superclass.

Answer

To modify the behavior of inherited methods.

Answer

To create a new instance of the superclass.

Question 37

Which code snippet correctly demonstrates method overriding?

Accepted Answer

class Animal { public void speak() { System.out.println("Default animal sound"); } } class Dog extends Animal { @Override public void speak() { System.out.println("Woof"); } }

Answer

class Animal { public void speak() { System.out.println("Default animal sound"); } } class Cat extends Animal { public void makeSound() { System.out.println("Meow"); } }

Answer

class Animal { private void speak() { System.out.println("Default animal sound"); } } class Dog extends Animal { public void speak() { System.out.println("Woof"); } }

Question 38

Which of the following is NOT an advantage of using interfaces?

Accepted Answer

They force implementing classes to have a specific state.

Answer

They promote code reusability and maintainability.

Answer

They enable loose coupling between classes.

Question 39

Which code snippet accurately implements an interface?

Accepted Answer

interface Animal { void speak(); } class Cat implements Animal { public void speak() { System.out.println("Meow"); } }

Answer

interface Animal { void speak(); } class Dog extends Animal { public void bark() { System.out.println("Woof"); } }

Answer

interface Animal { void speak(); } class Pig implements Animal { private void speak() { System.out.println("Oink"); } }

Question 40

What is the key distinction between a class and an interface?

Accepted Answer

A class can encapsulate both state and behavior, while an interface defines only method signatures and behavior.

Answer

An interface can have instance variables, but a class cannot.

Answer

A class can implement multiple interfaces, but an interface cannot extend multiple classes.

Question 41

Which code snippet demonstrates polymorphism?

Accepted Answer

Animal animal = new Dog(); animal.speak(); // Prints "Woof"

Answer

Dog dog = new Dog(); dog.speak();

Answer

Animal animal = new Cat(); animal.speak();

Answer

Cat cat = new Cat(); cat.meow();

Question 42

What is the primary purpose of the 'implements' keyword?

Accepted Answer

To declare that a class must implement the methods defined in an interface.

Answer

To declare that a class inherits from another class.

Answer

To declare that a variable will reference an object of a specific type.

Question 43

Which of the following best describes the nature of interfaces in object-oriented programming?

Accepted Answer

They define contracts that classes must adhere to, enabling code reusability and polymorphism.

Answer

They are abstract classes that cannot be instantiated directly.

Answer

They are classes that provide default implementations for commonly used methods.

Question 44

What is the primary purpose of the 'final' keyword when applied to a method in an interface?

Accepted Answer

To indicate that the implementing classes cannot override the method.

Answer

To force the implementing classes to override the method.

Answer

To make the method accessible only within the interface itself.

Question 45

What is a key benefit of polymorphism in object-oriented programming?

Accepted Answer

It allows objects of different classes to respond to the same method call in a uniform manner.

Answer

It eliminates the need for conditional statements, simplifying code.

Answer

It ensures that all classes are derived from a common base class.

Question 46

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

Accepted Answer

Interfaces can include concrete method implementations.

Answer

Interfaces cannot be instantiated directly.

Answer

Interfaces can define abstract methods.

Question 47

In object-oriented programming, what is the essence of Polymorphism?

Accepted Answer

Objects from diverse classes can react uniquely to identical method invocations.

Answer

Altering a variable's data type during runtime.

Answer

Creating multiple instantiations of an identical class.

Question 48

Within object-oriented programming, what is the paramount objective of an interface?

Accepted Answer

To establish a contract that classes must adhere to, ensuring they provide specific methods.

Answer

Encapsulating data and methods within a class.

Answer

Creating a new class that inherits from another class.

Question 49

Identify the key attribute of an interface:

Accepted Answer

Defines a set of methods that classes inheriting it must implement.

Answer

Can be instantiated as an object.

Answer

Serves as a blueprint for creating objects.

Question 50

What is the significance of method overriding in object-oriented programming?

Accepted Answer

To provide distinct implementations for the same method across different subclasses.

Answer

To invoke methods from a superclass.

Answer

To create new methods in a subclass.

Question 51

Which scenario exemplifies polymorphism in practice?

Accepted Answer

Creating a collection of diverse animal objects and invoking their 'makeSound()' method.

Answer

Creating an object of a specific animal class and invoking its 'makeSound()' method.

Answer

Constructing a generic method that accepts any object as input.

Question 52

When is it appropriate to use an anonymous inner class?

Accepted Answer

To implement an interface dynamically.

Answer

To generate a new object of an existing class.

Answer

To extend an abstract class.

Question 53

Identify a key limitation associated with interfaces:

Accepted Answer

They lack the ability to include implementation details.

Answer

They can only be implemented by a single class.

Answer

They cannot be extended.

Answer

They are restricted to defining only public methods.