code: private double distance(double[] center, double[] center2) {
  		double d = 0D;
  		for (int i = 0; i < center.length; i++) {
  			d += Math.pow((center[i] - center2[i]), 2);
  		}
  		return Math.sqrt(d);
  	}
docs: eclidean distance
  
  @param center
  @param center2
  @return