Quiz 8: Circularly Referential Data

Below is a class diagram for classes that represent a list of employees.
Each employee is a member of one or more group, and each group has a 
name and a list of employees in that group.

Define the Java classes that correspond to this class diagram and include
the constructors. Add methods that may be needed to make it possible to
define examples of data in this class hierarchy.


+-------------------------------------------------+
|              +-------------------+              |
|              |                   |              |
|              v                   |              v
|          +------+                |          +------+       
|          | ALoE |<-------------+ |          | ALoG |<-----------+
|          +------+              | |          +------+            |
|          +------+              | |          +------+            |
|             / \                | |             / \              |
|             ---                | |             ---              |
|              |                 | |              |               |
|     ----------------           | |     ----------------         |
|     |              |           | |     |              |         |
| +-------+   +----------------+ | | +-------+    +-------------+ |
| | MTLoE |   | ConsLoE        | | | | MTLoG |    | ConsLoG     | |
| +-------+   +----------------+ | | +-------+    +-------------+ |
| +-------+ +-| Employee first | | | +-------+  +-| Group first | |
|           | | ALoE rest      |-+ |            | | ALoG rest   |-+ 
|           | +----------------+   |            | +-------------+
|           |                      |            |
|           v                      |            v
|    +-------------+               |  +--------------+
|    | Employee    |               |  | Group        |
|    +-------------+               |  +--------------+
|    | String name |               |  | String name  |
+----| ALoG groups |               +--| ALoE members |
     +-------------+                  +--------------+

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