Java Polymorphism MCQs

Which of the following best describe polymorphism in Java?

A. Ability of different classes to be used interchangeably B. Process of creating multiple objects from a class C. Feature that allows different data types in a single variable D. Ability of different classes to be used interchangeably

View Answer

Correct Answer: )

Polymorphism in Java refers to the ability of different classes to be used interchangeably through a common interface.

Key Explanation

It enables flexibility and extensibility in code.
polymorphism is fundamental concept in object-oriented programming language
It promotes code reusability and abstraction.

Additional Information

Polymorphism is achieved through method overriding and interfaces in Java.
The ability to develop generic code that works with several object types is provided by polymorphism.
Compile-time polymorphism is achieved through method overloading.
Runtime polymorphism is achieved through method overriding.
Polymorphism is closely related to inheritance and abstraction.

Which keyword in Java is used to refer to the parent class within a subclass?

A. base B. parent C. super D. this

View Answer

Correct Answer: C)

The 'super' keyword is used to refer to the parent class within a subclass.

Key Explanation

It is often used to call overridden methods from the parent class.
It is used to access members of the parent class that are hidden by the subclass.
Super can also be used to call the parent class constructor.

Additional Information

The 'super' keyword is closely related to inheritance and method overriding.
Method chaining is made possible via the super keyword, which calls methods from both parent and child classes.
The 'super' keyword ensures that the correct method or constructor is invoked in the hierarchy.
Using 'super' helps in avoiding naming conflicts between parent and child class members.
It enhances code clarity and organization in class hierarchies.

What is the biggest reason for the use of polymorphism in Java?

A. Improved memory management B. Higher execution speed C. Enhanced code readability D. Code reusability and flexibility

View Answer

Correct Answer: D)

The biggest reason for the use of polymorphism in Java is its ability to achieve code reusability and flexibility.

Key Explanation

It allows classes to be designed to be extended and reused in various scenarios.
The ability to create general classes and more specialized classes that inherit and extend their behavior is made possible by polymorphism.
Changes made to the base class automatically affect its subclasses, reducing redundant code.

Additional Information

Code reusability is a fundamental concept in object-oriented programming (OOP).
Polymorphism promotes the 'open-closed' principle, where classes are open for extension but closed for modification
Software systems with polymorphism are more scalable and maintainable.
It simplifies the process of adding new features and functionalities to existing code.

What is the difference between method overloading and method overriding in Java?

A. Method overriding is used to provide different implementations of a method in different classes. B. Method overriding is used to create multiple methods with the same name but different parameters. C. Method overloading is a runtime concept, while method overriding is a compile-time concept. D. Method overloading allows defining multiple methods with the same name in a class.

View Answer

Correct Answer: D )

The key difference between method overloading and method overriding lies in the number and type of parameters.

Key Explanation

Method overloading involves defining multiple methods with the same name but different parameters in the same class.
Method overloading improves code readability and eliminates the need for multiple method names.
Overloaded methods are differentiated by the number or types of parameters they accept.

Additional Information

Method overriding is used in inheritance to provide a specific implementation of a method in a subclass.
It involves creating a method in the subclass that has the same name, return type, and parameters as a method in the parent class.
In Java, method overriding is necessary to implement polymorphism.

What is the primary purpose of the 'final' keyword in Java?

A. To define a constant variable B. To indicate the end of a code block C. To specify that a class cannot be instantiated D. To prevent a method from being overridden

View Answer

Correct Answer: D )

The 'final' keyword is used to indicate that a method should not be overridden by subclasses.

Key Explanation

When applied to a method, the 'final' keyword ensures that the method's implementation cannot be changed in any subclass.
When you want to ensure the same behavior across all subclasses, this is helpful.
It is commonly used in the context of security-sensitive or critical methods that should not be altered.

Additional Information

Using 'final' with methods can enhance code stability and reliability.
When a class has the designation 'final' sub classing is not permitted.
Applying 'final' to a variable makes it a constant that cannot be changed after its initial assignment.
Final methods cannot be overridden, final classes cannot be extended, and final variables cannot be reassigned.

What is the main advantage of runtime polymorphism in Java?

A. Stronger encapsulation of class members B. Early error detection during compilation C. Dynamic method resolution at runtime D. Improved code execution speed

View Answer

Correct Answer: C )

Runtime polymorphism allows the selection of the appropriate method implementation at runtime based on the actual object's type.

Key Explanation

It enables dynamic binding, where the correct method is determined during program execution.
Runtime polymorphism is achieved through method overriding and inheritance.
It supports flexible and extensible code, enhancing the modularity of the program.

Additional Information

Runtime polymorphism is a key feature of object-oriented programming languages.
It supports the 'open-closed' principle by enabling you to add new classes without changing the code already in place.
Dynamic method resolution is achieved through the virtual method table (VMT) or method table.
It's a crucial mechanism for achieving polymorphism and code reusability.

Which keyword is used in Java to achieve dynamic method dispatch?

A. dynamic B. super C. virtual D. dispatch

View Answer

Correct Answer: B )

The 'super' keyword is used in Java to achieve dynamic method dispatch or runtime polymorphism.

Key Explanation

Dynamic method dispatch involves selecting the appropriate method implementation at runtime based on the object's type.
The 'super' keyword helps in invoking overridden methods of the parent class from the subclass.
This is a crucial aspect of achieving polymorphism and maintaining code extensibility.

Additional Information

Dynamic method dispatch is also known as late binding or runtime binding.
super is a key feature of object-oriented programming languages that enables polymorphism.
The 'super' keyword is commonly used in overridden methods to call the parent class implementation before adding specific behavior.
Dynamic method dispatch contributes to the flexibility and adaptability of object-oriented code.

What is the primary role of the 'extends' keyword in Java?

A. To create an instance of a class B. To enable one class to inherit from another class C. To indicate a method's overriding status D. To allow a class to implement multiple interfaces

View Answer

Correct Answer: B )

The 'extends' keyword is used to indicate that a class is inheriting from another class in Java.

Key Explanation

Inheritance forms a hierarchical relationship between classes, enabling the reuse of code and properties.
A subclass inherits the fields and methods of its superclass through the 'extends' keyword.
Java supports single inheritance, meaning a class can only extend one superclass.

Additional Information

In order to achieve code reuse through inheritance, the 'extends' keyword is essential.
It establishes an 'is-a' relationship between the subclass and superclass.
The 'extends' keyword is essential for creating class hierarchies and implementing OOP principles.
In Java, a class can extend another class, but it can implement multiple interfaces.
Subclasses inherit both the attributes and behaviors (methods) of their superclasses.

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

A. To refer to the parent class B. To define constants C. To invoke static methods D. To create instances of a class

View Answer

Correct Answer: A )

The 'super' keyword is used in Java to refer to the parent class within a subclass.

Key Explanation

It's often used to call overridden methods from the parent class.
'Super' can access members of the parent class that are hidden by the subclass.
It's also used to call the parent class constructor from the subclass constructor.

Additional Information

Using 'super' enhances code clarity by explicitly indicating the source of a method or field.
'Super' is essential in achieving method overriding and dynamic method dispatch.
'Super' helps prevent naming conflicts between parent and child class members.
'Super' ensures proper method chaining and inheritance behavior.
It's a crucial component of object-oriented programming and class hierarchies.

What is the key difference between method overloading and method overriding in Java?

A. Method overloading allows changing the return type of a method. B. Method overriding is achieved using the 'super' keyword. C. Method overriding allows creating methods with the same name and parameters. D. Method overloading is determined at compile-time, while method overriding is determined at runtime.

View Answer

Correct Answer: C )

The key difference between method overloading and method overriding is that method overloading allows creating multiple methods with the same name and parameters in the same class.

Key Explanation

Method overloading is based on the number, type, and order of method parameters.
Method overloading provides flexibility by allowing different forms of the same method in the same class.
Method overloading is determined at compile-time through static polymorphism.

Additional Information

On the other hand, method overriding involves adding a method to a subclass that has the same name, inputs, and output as the parent class method.
Method overriding allows you to provide a specific implementation in the subclass.
It's determined at runtime through dynamic polymorphism.
The 'super' keyword is often used in overridden methods.

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What is the primary purpose of the 'dynamic binding' concept in Java?

A. To enable early error detection in the code B. To enhance code execution speed C. To allow flexible method invocation at runtime D. To prevent method overriding

View Answer

Correct Answer: C )

The primary purpose of dynamic binding in Java is to enable flexible method invocation at runtime.

Key Explanation

Dynamic binding ensures that the appropriate method implementation is selected based on the object's type.
Dynamic binding is an important feature in achieving polymorphism in object oriented programming language.
Dynamic binding is achieved through method overriding.

Additional Information

Dynamic binding contributes to the adaptability and versatility of software systems.
It makes it easier to write code that is extendable and can easily support new classes without changing the old code
The 'super' keyword is often used to invoke parent class methods in the context of dynamic binding.
Java program runtime behavior is improved through dynamic binding.
It is useful for writing readable and reusable code.

What is the difference between early binding and late binding in Java?

A. Early binding is used for static polymorphism, while late binding is used for dynamic polymorphism. B. Early binding is achieved through method overriding, while late binding is achieved through method overloading. C. Early binding is determined at runtime, while late binding is determined at compile-time. D. Early binding occurs with method calls to private methods, while late binding occurs with protected methods.

View Answer

Correct Answer: A )

The primary difference between early binding and late binding lies in the timing of method resolution.

Key Explanation

Early binding, also known as static binding, occurs at compile-time.
It includes resolving method calls according to the reference type rather than the object type.
Early binding is related to method overloading.

Additional Information

Early binding ensures better performance as the method resolution is known at compile-time.
Early binding is commonly used for method calls involving compile-time constants and private methods
Late binding, also known as dynamic binding, occurs at runtime.
It involves method calls being resolved based on the actual object type.
Late binding is important for achieving polymorphism through method overriding.
It provides flexibility and adaptability to the code.

What is the purpose of using the 'super' keyword within a constructor in Java?

A. To call a method in the subclass B. To indicate that the subclass constructor is using superclasses C. To create an instance of the parent class D. To initialize instance variables of the parent class

View Answer

Correct Answer: D )

The 'super' keyword is used within a constructor in Java to initialize instance variables of the parent class.

Key Explanation

When a subclass is created, its constructor can call the constructor of the parent class using 'super'.
This ensures that both the parent and child class instance variables are properly initialized.
The 'super' keyword must be the first statement within the constructor.

Additional Information

'Super' allows constructors in the subclass to reuse code from the parent class constructor.
It helps in achieving proper initialization of the class hierarchy.
Using 'super' within constructors promotes code organization and reduces redundancy.
Constructors with 'super' maintain the inheritance relationship between the classes.

Which keyword is used in Java to prevent a class from being subclassed?

A. private B. static C. final D. sealed

View Answer

Correct Answer: C )

The 'final' keyword is used in Java to prevent a class from being subclassed.

Key Explanation

Applying 'final' to a class indicates that it is the end of the inheritance hierarchy.
Such a class cannot have subclasses.
It's often used for classes that are complete and should not be extended.

Additional Information

'Final' classes can still extend other classes that are not 'final'.
The 'final' keyword is also used to create constant variables and prevent method overriding.
Using 'final' helps in ensuring the stability and immutability of certain class structures.
This is useful in scenarios where the class's behavior should not be altered or extended.

What concepts come under polymorphism in Java?

A. Static and dynamic binding B. Method overloading and method overriding C. Variable naming and method visibility D. Class encapsulation and inheritance

View Answer

Correct Answer: B )

Polymorphism in Java encompasses both method overloading and method overriding.

Key Explanation

Method overloading allows creating multiple methods with the same name but different parameters.
It is decided at the time of compilation and hence it is static polymorphism.

Additional Information

Method overriding involves creating a method in a subclass with the same name and parameters as in the parent class.
It's determined at runtime and contributes to dynamic polymorphism.
Polymorphism is vital for code extensibility and adaptability.

Which of the following statements about Java method overloading is true?

A. Method overloading involves creating methods with the same name and parameters in different classes. B. Method overloading allows creating methods with the same name but different return types. C. Method overloading is determined at runtime. D. Method overloading is a form of dynamic polymorphism.

View Answer

Correct Answer: B )

Java method overloading allows creating methods in the same class with the same name but different parameter lists.

Key Explanation

Overloaded methods must have different parameter lists, including a difference in the number or types of parameters.
The return type is not considered for method overloading.
Method overloading contributes to compile-time or static polymorphism.

Additional Information

Method overloading enhances code readability by allowing the use of intuitive method names.
It's helpful when you want to offer several different ways to carry out a same task.
Method overloading does not involve inheritance or subclasses.
Method overloading is a form of compile-time polymorphism.
Method overloading plays a role in designing user-friendly APIs.

What is the main benefit of using early binding in Java?

A. Dynamic method resolution B. Enhanced runtime flexibility C. Compile-time error detection D. Improved code execution speed

View Answer

Correct Answer: C )

The main benefit of using early binding in Java is the ability to detect errors at compile-time.

Key Explanation

Early binding ensures that method calls are resolved at compile-time.
If there are any issues with the method call, such as incorrect parameters or method name, they are detected during compilation.
This leads to early error detection and more reliable code.

Additional Information

Early binding is a form of static polymorphism that is determined at compile-time.
It improve efficiency of the code by resolving method calls beforehand.
Early binding is very useful for spotting errors before they can cause problems while the programme is being executed.
It promotes code correctness and maintainability.

What is the main difference between early binding and late binding?

A. Early binding is achieved through method overriding. B. Late binding occurs during method call syntax analysis. C. Early binding involves method resolution at runtime. D. Late binding occurs at compile-time.

View Answer

Correct Answer: A )

The main difference between early binding and late binding lies in when method resolution occurs.

Key Explanation

Early binding involves resolving method calls at compile-time.
Static polymorphism is used, frequently with method overloading, to achieve it.
Early binding ensures efficiency by determining the appropriate method at compile-time.

Additional Information

Late binding involves resolving method calls at runtime.
Dynamic polymorphism, frequently utilising method overriding, is used to achieve it.
In order to support polymorphism, late binding makes code more adaptable and flexible.
Dynamic binding is a key feature of object-oriented programming languages like Java.

In Java, what is the key role of the 'super' keyword in method overriding?

A. To invoke the static method in the subclass B. To create an instance of the superclass C. To access private methods in the subclass D. To call the overridden method in the superclass

View Answer

Correct Answer: D )

The 'super' keyword in method overriding is used to call the overridden method in the superclass.

Key Explanation

The 'super' keyword can be used to refer to the parent class's version of a method when a subclass overrides one from the superclass.
This allows the subclass to extend the behavior of the parent class while also retaining or enhancing the original behavior.

Additional Information

The 'super' keyword is important for achieving method chaining in overridden methods.
It makes sure that the method of the subclass preserves the behaviour of the superclass.
Using 'super' in method overriding enhances code maintainability and readability.
'Super' contributes to the consistency of the method hierarchy within an inheritance structure.

Which of the following statements is true about the 'final' keyword in Java?

A. A final method cannot be called from other classes. B. A final method can be overridden in subclasses. C. A final variable can be reassigned after its initial assignment. D. A final class can be extended by other classes.

View Answer

Correct Answer: D )

A final class in Java cannot be extended by other classes.

Key Explanation

Declaring a class as 'final' prevents other classes from inheriting from it.
When you want to make sure that a class's behaviour doesn't change, you frequently use it.
'Final' classes are complete and should not be altered through inheritance.

Additional Information

Final methods cannot be overridden in subclasses.
Final variables cannot be reassigned once they are given a value.
'Final' methods and classes contribute to code stability and reliability.
Using 'final' prevents unintended modifications to classes, methods, and variables.

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