public static List<String> divide_sentence(String str){
		List<String> list=new ArrayList<String>();
		list.clear();
		StringTokenizer token=new StringTokenizer(str, " , . ; : : + - * / @ ! & ( ) [ ]");
		
		while (token.hasMoreTokens()){
			list.add(token.nextToken());
		}
		
		return list;
	}