| Class | Description | 
|---|---|
| atom_t | An atom_t is a specialised LongHolder which decrements its atom's reference
 count when garbage-collected (finalized). | 
| BooleanHolder | A BooleanHolder is merely a Holder class for a boolean value. | 
| DoubleHolder | A DoubleHolder is merely a Holder class for a double value. | 
| engine_t | A engine_t holds a reference to a Prolog engine. | 
| fid_t | An fid_t holds the value of a frame id in the Prolog Engine. | 
| functor_t | A functor_t holds a reference to a Prolog functor_t in the Prolog engine. | 
| Int64Holder | An Int64Holder is merely a Holder class for an int64 value. | 
| IntHolder | An IntHolder is merely a Holder class for an Int value. | 
| LongHolder | A Long Holder merely holds a long value. | 
| module_t | A module_t is a PointerHolder type which holds a reference to a Prolog
 module_t reference. | 
| ObjectHolder | A ObjectHolder is merely a Holder class for an Object reference (or null). | 
| PointerHolder | A PointerHolder is a trivial extension of a LongHolder. | 
| predicate_t | A predicate_t is a PointerHolder class whose value is a reference to a Prolog
 predicate_t. | 
| Prolog | This class consists only of constants (static finals) and static native
 methods. | 
| qid_t | A qid_t holds a reference to a Prolog qid_t. | 
| StringHolder | A StringHolder is merely a Holder class for a String value. | 
| term_t | A term_t is a simple class which mirrors the term_t type in the Prolog FLI. |