Marcel is implementing password policy. So when a user changes his password, it must be different than the previous 15 passwords. These previous passwords are stored in the databases as hashed strings. Of course we're trying to compare the hashed values and not the plain one.
But you can validate the plain new password against the hashed previous ones. In java,
get the IMendixObject with the password to check, then retrieve the proper member (getMember) and cast it to MendixHashString. The casted object has the methods to check your plain password against.