public abstract class Vehicle {
	
	public abstract void accept(VehicleVisitor visitor);
	
	public abstract int getType();
	
	// to enable cached types, uncomment the two commented lines below
	
	// private final int cachedType = getType();
	
	public int getCachedType() {
		// return cachedType; /*
		throw new UnsupportedOperationException(); // */
	}
	
}