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## Inheritance

- More general class = superclass
- More specialized class = subclass
- Subclass supports all method interfaces of superclass (but implementations may differ)
- Subclass may have added methods, added state
- Subclass inherits from superclass
- Example: `ForwardedMessage` inherits from `Message`
- Example: `Greeting` does not inherit from `Message` (Can't store greetings in mailbox)

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