Java Classes and Objects Fundamentals Quiz

16 Questions

Which keyword is used to create an object of a class in Java?

new

What is a class in Java?

A user defined data type

What are the variables defined within a class called?

Instance variables

What is contained within a class in Java?

All of the above

What does the 'Box mybox = new Box();' line of code do?

Creates an instance of the Box class

What is 'vol' in the line 'double vol;' used for?

Initializing a variable

What is the purpose of the 'volume()' method in the Box class?

To compute and display the volume of the box

In the given program, what is the purpose of the 'Box mybox = new Box();' statement?

To allocate memory for a new Box object

What does the 'volume' method with a return type of 'double' do in the Box class?

It computes and returns the volume of the box

What does the 'square()' method without parameters do?

It computes and returns the square of 10

What is the purpose of the 'volume(double w, double h, double d)' method in the Box class?

To compute and return the volume of a box

What is allocated when 'Box mybox = new Box();' is executed?

Memory for a new Box object

What is computed and returned by the 'volume()' method with a return type of 'double' in the Box class?

The product of width, height, and depth

What is displayed by the 'System.out.println("Volume is " + vol);' statement?

'Volume is' followed by the product of width, height, and depth

What does the 'square(int i)' method with a return type of 'int' do?

It computes and returns $i * i$.

What does the 'volume()' method in Box class do?

It computes volume for given width, height, and depth.

Study Notes

Creating Objects in Java

The keyword new is used to create an object of a class in Java.

Classes in Java

A class in Java is a blueprint for creating objects that contain data and behavior.
A class in Java typically contains variables and methods.

Variables in Java

Variables defined within a class are called data members or fields.

Class Components in Java

A class in Java can contain variables (data members or fields) and methods.

Object Creation in Java

The line of code Box mybox = new Box(); creates a new object of the Box class and assigns it to the mybox variable.

Variable Usage in Java

The double vol; declaration is used to declare a variable to store the volume of a box.

Method Purpose in Java

The volume() method in the Box class computes and returns the volume of a box.
The square() method without parameters is used to calculate the square of a number.
The volume(double w, double h, double d) method in the Box class is used to calculate the volume of a box with given width, height, and depth.
The square(int i) method with a return type of int calculates the square of a given integer.

Memory Allocation in Java

When Box mybox = new Box(); is executed, memory is allocated for the mybox object.

Method Return in Java

The volume() method with a return type of double in the Box class computes and returns the volume of a box.

Printing Output in Java

The System.out.println("Volume is " + vol); statement displays the volume of a box.

Test your knowledge about the fundamentals of classes, objects, and methods in Java. Learn about the definition of classes, the creation of objects using the 'new' keyword, and the relationship between classes and objects. Understand how classes serve as templates for objects, and how they are declared using the 'class' keyword.

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