Java Program to Calculate Area of Circle

1. Simple Java program to calculate Area of Circle.

public class CircleArea1{
    public static void main (String[] args){
        
        double radius =12;
        
        System.out.println ("Radius = "+radius);
        
        //calculate area
        double area = 3.14 * (radius * radius);
        
        System.out.println ("Area of a circle = "+area);
    }
}

Save this file as'CircleArea1.java'
Compile: $javac CircleArea1.java
Execution: $java CircleArea1
Output:

Radius = 12.0
Area of a circle = 452.16

2. Write a Java program to calculate the area of circle using object and class method.

class Circle1{
    //creating method
    public void m1(){
        
        double radius =325;
        
        System.out.println ("Radius = "+radius);
        
        //calculate area
        double area = 3.14 * (radius * radius);
        
        System.out.println ("Area of a circle = "+area);
    }
}

public class CircleArea2{
    public static void main (String[] args){
        //creating new object
        Circle1 obj = new Circle1();
        
        //calling method
        obj.m1();
    }
}

Save this file as 'CircleArea2.java'
Compile: $javac CircleArea2.java
Execute: $java CircleArea2
Output:

Radius = 325.0
Area of a circle = 331662.5