I am trying to retrieve groups for a given MS Active Directory user
using Java LDAP. When searching, I use the memberOf filter. The
Default Users default group doesn't appear in the search results.
Is this expected?
Yes, this is an expected behaviour. This is default domain group when the user is created/moved to the domain, and is called the PrimaryGroup.
This is a special group which every user is a part of by default, whenever he/she is added/moved to the domain.
Are there any additional options I should use to get this group as
If you want to read this using LDAP query, you can always query the user's PrimaryGroup attribute. It'd give you the value for the user as to which domain he belongs.
Sample query how you can achieve the same in Powershell is listed below:
Get-ADUser -Identity "<user-id>" -Properties * | Select sAMAccountName, PrimaryGroup