public static List UniteList(List x,List y){
		if ((x == null) || (x.size() == 0) || (y == null) || (y.size() == 0)) {
			return new ArrayList();
		}
		if(x.size()>y.size()){
		   x.retainAll(y); 
		   return x;
		}else{
		   y.retainAll(x); 
		   return y;
		}
	}