algorithm to calculate b splines

Bspline

package testproject.test;

import java.awt.Graphics;

public class Bspline {

    double[][]       P;
    double[]         T;
    int             _k = 3;
    
    public Bspline() {
        P = new double[3][2];
        P[0][0] = 100; P[0][1] = 100;
        P[1][0] = 47; P[1][1] = 68;
        P[2][0] = 123; P[2][1] = 284;
        
        update();
    }

    private void update() {
        if(P.length < 2)
            return;
        //_k = Math.min(4, P.length);
        T = new double[_k+P.length+1];
        
        double d = 1.0/(1+T.length - 2*_k);
        int i;
        for(i = _k ; i < T.length-_k; i++){
            T[i] = (i+1-_k)*d;
        }for(; i < T.length; i++){
            T[i] = 1;
        }
    }
    
    private double basisFunc(int i, int k, double t){
        if(k == 0){
            if(T[i] <= t && t < T[i+1])
                return 1;
            return 0;
        }
        double a = (T[i+k]-T[i]) == 0 ? 0 : (t-T[i])/(T[i+k]-T[i]);
        double b = (T[i+k+1]-T[i+1]) == 0 ? 0 : (T[i+k+1]-t)/(T[i+k+1]-T[i+1]);
        if(Double.isNaN(a) || Double.isNaN(b) || Double.isInfinite(a) || Double.isInfinite(b))
            System.err.println("should not happen");
        return a*basisFunc(i, k-1, t) + b * basisFunc(i+1, k-1, t);
    }
    
    private double[] DeBoor(double t){
        double[] V = new double[2];
        for(int i = 0; i < P.length; i++){
            double scale = basisFunc(i, _k, t);
            V[0] += P[i][0] * scale;
            V[1] += P[i][1] * scale;
        }
        return V;
    }
    
    public void calculatePath(Graphics g){
        if(P.length < 2){
            return; // zu wenige punkte um ein pfad zu zeichnen
        }
        double[] v = new double[2];
        /*
        double delta = (T[P.length+1]-T[_k])/32.0;
        for(double t = T[_k]; t < T[P.length+1]; t += delta ){
        /*/
        double delta = 1/32.0;
        for(double t = 0; t < 1; t += delta ){
        //*/
            double[] p = DeBoor(t);
//            System.out.println(p[0]+"|"+p[1]);
            if(v != null){ g.drawLine((int)v[0], (int)v[1], (int)p[0], (int)p[1]); }
            v = p;
        }
    }
}