Java convert karthesian coordinate to spherical back and forth failure

Point3d_karthesian.java

package javax.vecmath;

import com.sun.corba.se.impl.interceptors.PICurrent;

public class Point3d_karthesian extends Point3d {
	public Point3d_karthesian() {
		super();
	}

	public Point3d_karthesian(double[] arg0) {
		super(arg0);
	}

	public Point3d_karthesian(Point3d arg0) {
		super(arg0);
	}

	public Point3d_karthesian(Point3f arg0) {
		super(arg0);
	}

	public Point3d_karthesian(Tuple3d arg0) {
		super(arg0);
	}

	public Point3d_karthesian(Tuple3f arg0) {
		super(arg0);
	}
	
	public Point3d_karthesian(double arg0, double arg1, double arg2) {
		super(arg0, arg1, arg2);
	}

	public double getOffset() {
		return z;
	}

	/**
	 * Convert to radius,phi,theta point
	 * 
	 * @see https://de.wikipedia.org/wiki/Kugelkoordinaten#.C3.9Cbliche_Konvention
	 * @return Point3d_spherical
	 */
	public Point3d_spherical toSpherePoint() {
		double radius, phi, theta;
		double z = this.z;
		
		radius	= Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2) + Math.pow(z, 2));
		
		/*
		if(x > 0) {
			phi = Math.atan((y / x));
		} else if(x == 0) {
			phi = Math.signum(y) * (Math.PI / 2);
		} else if(x < 0 && y >= 0) {
			phi = Math.atan((y / x)) + Math.PI;
		} else if(x < 0 && y < 0) {
			phi = Math.atan((y / x)) - Math.PI;
		} else {
			phi = 0;
			System.err.println("Huston we got a problem!");
		}
		*/
		phi		= Math.atan2(y, x);
		
		if(radius != 0) {
			theta	= Math.acos((z / radius));
		} else {
			theta	= 0d;
			//theta	= Math.acos(z);
		}
		
		return new Point3d_spherical(radius, phi, theta);
	}
}

Point3d_spherical.java

package javax.vecmath;

public class Point3d_spherical {
	protected double	radius,
						phi,
						theta;

	public Point3d_spherical() {
		
	}

	public Point3d_spherical(double radius, double phi, double theta) {
		this.radius	= radius;
		this.phi	= phi;
		this.theta	= theta;
	}

	public String toString() {
		return "(" + radius + ", " + phi + ", " + theta + ")";
	}
	
	/**
	 * Convert to x,y,z point
	 * 
	 * @see https://de.wikipedia.org/wiki/Kugelkoordinaten#.C3.9Cbliche_Konvention
	 * @return Point3d_karthesian
	 */
	public Point3d_karthesian toPoint3d() {
		double x, y, z;
		
		x = radius * Math.sin(theta) * Math.cos(phi);
		y = radius * Math.sin(theta) * Math.sin(phi);
		z = radius * Math.cos(theta);
		
		return new Point3d_karthesian(x, y, z);
	}

	public double getRadius() {
		return radius;
	}

	public void setRadius(double radius) {
		this.radius = radius;
	}

	public double getPhi() {
		return phi;
	}

	public void setPhi(double phi) {
		this.phi = phi;
	}

	public double getTheta() {
		return theta;
	}

	public void setTheta(double theta) {
		this.theta = theta;
	}
}

Runner.java

import javax.vecmath.Point3d_karthesian;
import javax.vecmath.Point3d_spherical;

public class Runner {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		new Runner();
	}
	
	public Runner() {
		Point3d_karthesian	point	= new Point3d_karthesian(10, 0, 0);
		Point3d_spherical	sphere	= point.toSpherePoint();
		Point3d_karthesian	reverse	= sphere.toPoint3d();
		
		System.out.printf("Original point : %s\n", point);
		System.out.printf("Sphere   point : %s\n", sphere);
		System.out.printf("Reverse  point : %s\n", reverse);
	}
}

Stdout

Original point : (10.0, 0.0, 0.0)
Sphere   point : (10.0, 0.0, 1.5707963267948966)
Reverse  point : (10.0, 0.0, 6.123233995736766E-16)