Java Programming

Hey, i need help making a method that does the newton rhapson method;
public static double newton(Polynomial p, double x0){
}
newton rhap method is X(i+1)=Xi-(f(Xi)/(f '(Xi)) (Xi is initial x0)
*the answer should return when Xi - X(i-1) < 10^ -8

Polynomial is already defined as an array that just lists the coefficients of the polynomial.(it is a object)
i have already made methods that can
1.evaluate polynomials,
2.find degree of polynomials
3. find derivative of polynomials,
4, add polynomials,
5. multiply polynomials

But i really need help with this mwthod....help please