对于空字符串split（）操作获取的数组的长度为1解释

public  String[] split(CharSequence input,  int  limit) {
        int  index =  0 ;
        boolean  matchLimited = limit >  0 ;
        ArrayList matchList =  new  ArrayList();
        Matcher m = matcher(input);

        // Add segments before each match found
        while (m.find()) {
            if  (!matchLimited || matchList.size() < limit -  1 ) {
                String match = input.subSequence(index, m.start()).toString();
                matchList.add(match);
                index = m.end();
            }  else  if  (matchList.size() == limit -  1 ) {  // last one
                String match = input.subSequence(index,
                                                 input.length()).toString();
                matchList.add(match);
                index = m.end();
            }
        }

        // If no match was found, return this
        if  (index ==  0 )
            return  new  String[] {input.toString()};

这是 split方法的源码。。一看就明白。。因为 正则 匹配不到 字符。。就直接返回一个数组 、数组中包着 空字符串 所以他的长度是1