code: public double distance(Vector o) {
          return Math.sqrt(NumberConversions.square(x - o.x) + NumberConversions.square(y - o.y) + NumberConversions.square(z - o.z));
      }
docs: Get the distance between this vector and another. The value of this
  method is not cached and uses a costly square-root function, so do not
  repeatedly call this method to get the vector's magnitude. NaN will be
  returned if the inner result of the sqrt() function overflows, which
  will be caused if the distance is too long.
  
  @param o The other vector
  @return the distance