+----------------+
|     <<abstract>>     |
|       Shape        |
+----------------+
|                    |
| + getArea(): double (abstract) |
| + display()                |
+----------------+
          ▲
          │
    +-----+-----+-----+
    |           |     |
+----------+ +----------+ +----------+
|  Circle  | | Rectangle| | Triangle |
+----------+ +----------+ +----------+
| -radius  | | -width   | | -sideA   |
|          | | -height  | | -sideB   |
| +getArea()| | +getArea()| | -sideC   |
+----------+ +----------+ | +getArea()|
                           +----------+