Java Program to Find the Perimeter of a Circle

For a given circle with radius "r", write a Java program to find the perimeter of that circle. The circumference is also known as the perimeter. It's the distance around a circle.

Circumference is given by the formula C = 2?r where, pi/? = 3.14 and r is the radius of the circle ?

Example Scenario

Input: radius = 5
Output: perimeter = 31.400000000000002 

2 * 3.14 * 5 = 31.428571428571427

By Defining Constant Value for PI

In this Java program, we define the value of PI as a constant and find the perimeter of circle using it.

public class PerimeterOfCircle {
   // defining constant 
   static final double PICONST = 3.14;
   public static void main(String args[]) {
      double my_radius, my_perimeter;
      my_radius = 5;
      System.out.println("The radius of the circle is defined as " +my_radius);
      my_perimeter = PICONST * 2 * my_radius;
      System.out.println("The perimeter of Circle is: " + my_perimeter);
   }
}

Output

The radius of the circle is defined as 5.0
The perimeter of Circle is: 31.400000000000002

Using Math.PI

In the following example, we use the Math.PI to calculate the perimeter of the circle.

public class PerimeterOfCircle {
   public static void main(String args[]) {
      double my_radius, my_perimeter;
      my_radius = 7;
      System.out.println("The radius of the circle is defined as " + my_radius);
      my_perimeter = Math.PI * 2 * my_radius;
      System.out.println("The perimeter of Circle is: " + my_perimeter);
   }
}

Output

The radius of the circle is defined as 7.0
The perimeter of Circle is: 43.982297150257104