# 1. Introduction

Calculating the area of a circle is a common programming task that allows beginners to practice using mathematical operations, constants, and user input in Java. The formula to calculate the area of a circle is *Area = π * r²*, where *π* represents the mathematical constant pi, and *r* represents the radius of the circle.

# 2. Program Steps

1. Import the *Scanner* class from the *java.util* package for user input.

2. Define the main class named *AreaOfCircle*.

3. Inside the main class, define the *main* method.

4. Inside the *main* method, create an object of the *Scanner* class to take user input.

5. Prompt the user to enter the radius of the circle and store it in a variable.

6. Calculate the area of the circle using the formula *Area = π * r²*.

7. Print the calculated area to the console.

# 3. Code Program

```
import java.util.Scanner; // 1. Importing Scanner class for user input
public class AreaOfCircle { // 2. Defining the main class
public static void main(String[] args) { // 3. Defining the main method
Scanner input = new Scanner(System.in); // 4. Creating Scanner object to take user input
System.out.print("Enter the radius of the circle: "); // 5. Prompting user for the radius
double radius = input.nextDouble(); // Storing the radius in variable radius
double area = Math.PI * Math.pow(radius, 2); // 6. Calculating the area using the formula Area = π * r²
System.out.println("The area of the circle with radius " + radius + " is: " + area); // 7. Printing the calculated area
input.close(); // Closing the Scanner object to avoid memory leak
}
}
```

### Output:

Enter the radius of the circle: 5 The area of the circle with radius 5.0 is: 78.53981633974483

# 4. Step By Step Explanation

– Step 1: The *Scanner* class from the *java.util* package is imported to take user input.

– Step 2: The main class *AreaOfCircle* is defined.

– Step 3: The *main* method, which serves as the entry point of the Java program, is defined inside the main class.

– Step 4: An object of the *Scanner* class named "input" is created for reading user input.

– Step 5: The user is prompted to enter the radius of the circle, *5*, which is then stored in the variable *radius*.

– Step 6: The area of the circle is calculated using the formula *Area = π * r²*, where *π* is represented by *Math.PI* and *r* is the value stored in the variable *radius*. The result, *78.53981633974483*, is stored in the variable *area*.

– Step 7: Finally, the calculated area of the circle is printed to the console.

– The *Scanner* object is then closed to prevent resource leak.