How to add main method to this, to check if it works.

[Laura Rubyte]

Hi , I have this code :

public class Rootapproximation
{
	/**
	Constructs a root approximator for a given number
	aNumber the number from which to extract the square root
	(Precondition: aNumber >= 0)
	 */
	public Rootapproximation(double aNumber)
	{
		a = aNumber;
		xold = 1;
		xnew = a;
	}
	/**
	Compute a better guess from the current guess.
	returns the next guess
	 */
	public double nextGuess()
	{
		xold = xnew;
		if (xold != 0)
		{
			xnew = (xold + a / xold) / 2;
		}
		return xnew;
	}
	/**
	Compute the root by repeatedly improving the current
	guess until two successive guesses are approximately equal.
	@return the computed value for the square root
	 */
	public double getRoot()
	{
		while (!Numeric.approxEqual(xnew, xold))
		{
			nextGuess();
		}
		return xnew;
	}
	private double a; // the number whose square root is computed
	private double xnew; // the current guess
	private double xold; // the old guess
}

And I need to test programm by addinf a main method and the calling getRoot method with a parameter to set result.

I know that i have to create a main method that would call the written function, but have no idea how to do it. Any help appreciated.thanks

[Greg Brannon]

As you said, there are at least 2 approaches: you can add a main() method to the existing class file, or you can create another class file whose sole function is to test the class file you posted. In either case, the main() method would look something like:

public static void main( String[] args )
{
   // define aNumber

   Rootapproximation test = new Rootapproximation( aNumber );
}

How you get aNumber or the other things you might do with the test instance to test it thoroughly are up to you.

[Campbell Ritchie]

Welcome to the Ranch

Once you have the root approximation object Greg showed you, you can call its gteRoot() method and use the result however you wish.