code: public Vector getSpinVector(double theta, double phi) {
          Vector spinvector = new Vector(3);
          spinvector.vector[0] = Math.sin(theta) * Math.cos(phi);
          spinvector.vector[1] = Math.sin(theta) * Math.sin(phi);
          spinvector.vector[2] = Math.cos(phi);
          return spinvector;
      }
docs: Calculates a spin vector by a direction specified by theta and phi