public static <E> String combine2String(E[] a, String delimiter){
		if(a == null){
			return null;
		}
		StringBuilder sb = new StringBuilder();
		int length = a.length;
		int index = 0;
		while(index < length){
			sb.append(a[index++]);
			if(index<length)
				sb.append(delimiter);
		}
		return sb.toString();
	}