previous | start | next

## Preconditions

    /**

       Remove message at head

       @return the message at the head

       @precondition size() > 0

    */

    Message removeFirst()

    {

       return (Message)elements.remove(0);

    }

- What happens if precondition not fulfilled?
- `IndexOutOfBoundsException`
- Other implementation may have different behavior

previous | start | next