**Thread Reference can have any of these objects.
| Name | Type | Parent | Since | Detail |
| ForkJoinWorkerThread | Class | java.lang.Thread | 1.7 | Link |
| InheritableThreadLocal | Class | java.lang.ThreadLocal | 1.2 | Link |
| Thread | Class | java.lang.Object | 1.0 | Link |
| Thread.State | Class | java.lang.Enum | 1.5 | Link |
| ThreadDeath | Class | java.lang.Error | 1.0 | Link |
| ThreadGroup | Class | java.lang.Object | 1.0 | Link |
| ThreadLocal | Class | java.lang.Object | 1.2 | Link |