Replace Conditional with Polymorphism

You have a conditional that chooses different behavior depending on the type of an object.

Move each leg of the conditional to an overriding method in a subclass. Make the original method abstract.

	double getSpeed() {
		switch (_type) {
			case EUROPEAN:
				return getBaseSpeed();
			case AFRICAN:
				return getBaseSpeed() - getLoadFactor() * _numberOfCoconuts;
			case NORWEIGIAN_BLUE:
				return (_isNailed) ? 0 : getBaseSpeed(_voltage);
		}
		throw new RuntimeException ("Should be unreachable");
	}

For more information see page 255 of Refactoring

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