To make a square root function

Question 40 : Write a program in Java to make a function that calculates the square root of a number given by the user.

Java Program : 

import java.io.*;

class sqrt_function

{

 static void main()throws IOException

 {

     BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

     int i;

     double a,b=2,c=0;

     System.out.print("Enter a number : ");

     a=Double.parseDouble(br.readLine());

     for(i=1;i<=10;i++)

     {

        c=(a/b);

        b=(c+b)/2;

     }

     System.out.print("\nSquare Root of "+a+" = "+b);     

    }

}