- [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.

* <a href="http://www.exampledepot.com/egs/java.lang/IsJavaId.html">more info.</a>
     */
    public static boolean isJavaIdentifier(String s) {
        if (isEmpty(s) || !Character.isJavaIdentifierStart(s.charAt(0))) {
            return false;
        }
        for (int i = 1; i < s.length(); i++) {
            if (!Character.isJavaIdentifierPart(s.charAt(i))) {
                return false;
            }
        }
        return true;
    }
    public static boolean isContains(String values, String value) {
        return isNotEmpty(values) && isContains(COMMA_SPLIT_PATTERN.split(values), value);
    }
    public static boolean isContains(String str, char ch) {
        return isNotEmpty(str) && str.indexOf(ch) >= 0;
    }
    public static boolean isNotContains(String str, char ch) {
        return !isContains(str, ch);
    }
    /**
     * @param values
     * @param value
     * @return contains
     */
    public static boolean isContains(String[] values, String value) {
        if (isNotEmpty(value) && ArrayUtils.isNotEmpty(values)) {
            for (String v : values) {