- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.4
* Operating System version: Darwin Kernel Version 18.7.0
* Java version: 1.8.0_181-b13)

### Steps to reproduce this issue

1. invoke `StringUtils.split("d,1,2,4", 'a')`
2. invoke `"d,1,2,4".split("a")`

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

`StringUtils.split("d,1,2,4", 'a')` should return `["d,1,2,4"]` just like `"d,1,2,4".split("a")`.

### Actual Result

empty array.

}
    public static String[] delimitedListToStringArray(String str, String delimiter, String charsToDelete) {
        if (str == null) {
            return new String[0];
        } else if (delimiter == null) {
            return new String[]{str};
        } else {
            List<String> result = new ArrayList();
            int pos;
            if ("".equals(delimiter)) {
                for (pos = 0; pos < str.length(); ++pos) {
                    result.add(deleteAny(str.substring(pos, pos + 1), charsToDelete));
                }
            } else {
                int delPos;
                for (pos = 0; (delPos = str.indexOf(delimiter, pos)) != -1; pos = delPos + delimiter.length()) {
                    result.add(deleteAny(str.substring(pos, delPos), charsToDelete));
                }
                if (str.length() > 0 && pos <= str.length()) {
                    result.add(deleteAny(str.substring(pos), charsToDelete));
                }
            }
            return toStringArray((Collection) result);
        }
    }
    public static String arrayToDelimitedString(Object[] arr, String delim) {
        if (ArrayUtils.isEmpty(arr)) {
            return "";
        } else if (arr.length == 1) {
            return nullSafeToString(arr[0]);