public class RootFinder {
    // Java version, based on Numerical Recipes, p. 354
    public static final int JMAX= 40;       // Maximum number of bisections
    public static final double ERR_VAL= -10E10;
    public static int j;
    
    public static double rtbis(MathFunction func, double x1, double x2, double xacc) {
        double dx, xmid, rtb;
        double f= func.f(x1);
        double fmid= func.f(x2);
        if (f*fmid >= 0.0) {
            System.out.println("Root must be bracketed for bisection");
            return ERR_VAL;
        }
        // Orient search so f>0 lies at x + dx
        if (f < 0.0) {
            dx= x2 - x1;
            rtb= x1;
        }
        else {
            dx= x1 - x2;
            rtb= x2;
        }
     
        for (j=0; j < JMAX; j++) {
            dx *= 0.5;
            xmid= rtb + dx;
            fmid= func.f(xmid);
            if (fmid <= 0.0)
                rtb= xmid;
            if (Math.abs(dx) < xacc || fmid == 0.0) {
        		System.out.println("\nBisection iterations: "+ j);
                return rtb;
            }
        }
        System.out.println("Too many bisections");
        return ERR_VAL;
    }
}