Java Classes and Object-Oriented Programming Quiz

In Java, what is inheritance and how is it implemented?

• Inheritance is a mechanism in which one class acquires the properties and behaviors of another class. It is implemented using the 'extends' keyword.

• Inheritance is implemented using the 'include' keyword.

• Inheritance is a mechanism to hide the properties and behaviors of another class.

• Inheritance is a mechanism to create new classes from existing classes.

Explain the concept of method overriding in Java with an example.

• When a subclass provides a different implementation of a method that is not provided by its parent class.

• When a subclass provides a specific implementation of a method that is already provided by its parent class.

• Method overriding is when a subclass inherits a method from its parent class without any changes.

• Method overriding is not allowed in Java.

What is abstraction in Java and how is it achieved?

• Using abstract classes and interfaces

• By avoiding encapsulation

• Using concrete classes and inheritance

• Through polymorphism and overloading

Give an example of using an abstract class in Java.

• Creating an abstract class named Shape with an abstract method calculateArea()

• Using an abstract class named Person with only private methods

• Creating an abstract class named Animal with a concrete method eat()

• Defining an abstract class Car with no abstract methods

What is a constructor in Java and how is it different from a method?

• A constructor initializes objects, has the same name as the class, and does not have a return type. It is automatically called when an object is created, while a method is called explicitly to perform a specific task.

• A constructor is used to perform specific tasks, has a different name than the class, and is automatically called when an object is created

• A constructor creates new variables, has a different name than the class, and has a return type

• A constructor initializes objects, has the same name as the class, and has a return type

What are instance variables in Java and how are they different from local variables?

• Instance variables are declared within a method, constructor, or block, while local variables are declared within a class.

• Instance variables are declared with the 'var' keyword, while local variables are declared with the 'let' keyword.

• Instance variables are declared within a class but outside any method, constructor, or block, while local variables are declared within a method, constructor, or block and are only accessible within that scope.

• Instance variables are only accessible within a method, constructor, or block, while local variables are accessible throughout the class.

Provide an example of using instance variables in a Java class.

• Creating a class called 'Animal' with instance variables like 'species', 'weight', and 'age'.

• Creating a class called 'Book' with instance variables like 'title', 'author', and 'publisher'.

• Creating a class called 'Employee' with instance variables like 'name', 'salary', and 'department'.

• Creating a class called 'Car' with instance variables like 'model', 'color', and 'year'.