public static String trim(String str) {
        return str == null ? null : str.trim();
    }
<pre>
StringUtils.trim(null)          = null
StringUtils.trim("")            = ""
StringUtils.trim("     ")       = ""
StringUtils.trim("abc")         = "abc"
StringUtils.trim("    abc    ") = "abc"
</pre>

@param str the String to be trimmed, may be null
@return the trimmed string, {@code null} if null String input
core/common/src/main/java/com/alipay/sofa/rpc/common/utils/StringUtils.java