import java.util.Scanner;
/*******************************************************************************/
/**
 * This is an improved version that uses a main program to invoke a class
 * that contains the Newton code.  The previous versions were done as simply
 * programs so as to concentrate on the loop structure and control of the flow
 * of execution.  This would be a more proper Java version of such a program.
 *
 * @author Duncan Buell
 * 4 February 2008
**/

public class MySquareRootMain3
{
  public static void main (String[] args)
  {
    double epsilon,root,x;
    Scanner console = new Scanner(System.in);
    MySquareRoot rootFinder = new MySquareRoot();

// Notice how much code is involved just in getting the values input from the
// user.  There's a lot of effort that goes in to making sure that we are not
// going to crash due to faulty input.  Even at that, we have not tested to
// make sure the user has actually input a ***number*** and not text characters.
    System.out.println("Enter the tolerance epsilon for successive approximations: ");
    epsilon = console.nextDouble();
    if(epsilon <= 0)
    {
      System.out.println("ERROR:  Input value " + epsilon + " for epsilon is not positive");
      System.exit(0);
    }

    System.out.println("Enter the number for which to take the square root: ");
    x = console.nextDouble();
    if(x <= 0)
    {
      System.out.println("ERROR:  Input value " + x + " for x is not positive");
      System.exit(0);
    }

    System.out.println("Compute the square root of " + x);
    System.out.println("Stop when the difference between successive approximations is < " + epsilon);




// There's only one line of the 'do the work' part of the program.
    root = rootFinder.findRoot(x,epsilon);



// And then there is a lot of output to make sure that humans understand what's been done.
    System.out.println("Approximate square root of " + x + " is " + root);
    System.out.println("Built in function says root of " + x + " is " + Math.sqrt(x));
    System.out.println("The discrepancy is " + Math.abs(Math.sqrt(x) - root));

  }
} // public class MySquareRootMain3