if you don’t want to use PSUtilities, you can use a branch and regular expressions:
branch on /instring
/$/
/+$/
The first expression (which would appear in the label on the branch step, and would include the slashes) will match a string which contains exactly one digit.
The second expression will match a string which is composed of nothing but digits.
For those unfamiliar with regular expressions, the second one above can be translated as
match any string beginning with (specified by the ^) one or more (specified by the +) characters falling in the range of 0-9 (specified by [0-9]) followed by the end of string (specified by the $).
#webMethods#Integration-Server-and-ESB#Flow-and-Java-services