Struct classes are Java classes with public attributes and no modeled methods (It is the Java equivalent of a C++ struct.). They allow for the grouping of domain definitions and other struct classes to form programmatic record definitions.
Typically, struct classes are used as arguments to operations of entity and process classes. Structs are used to 'package' arguments in order to avoid long argument lists. Struct classes can also aggregate each other; these aggregations turn into struct members.
For example, in the case of a bank account entity, the parameters to a read operation would consist of a key struct and a details struct. The key struct might contain a single field for the account number. The details struct might have several fields including Name, Balance, etc.
Struct classes have a stereotype of struct.