PizzaService Class for PSE homework

PizzaService.java

import java.util.HashMap;

/**
 * @author Stefan
 */
public class PizzaService {
	public double calculatePizzaCost(int numberOfPizza, String typeOfPizza) throws IllegalArgumentException {
		double[] extraCost = {4.3, 3.75, 2.5, 1.75};
		HashMap<String, Number> typeToIndex = new HashMap<String, Number>();
		
		typeToIndex.put("thunfisch", 0);
		typeToIndex.put("salami", 1);
		typeToIndex.put("paprika", 2);
		typeToIndex.put("zwiebel", 3);
		
		if (!typeToIndex.containsKey(typeOfPizza.toLowerCase())) {
			throw new IllegalArgumentException("Ungültiger Pizza-Typ");
		}
		
		return ((4.35 + 0.65 + extraCost[typeToIndex.get(typeOfPizza.toLowerCase()).intValue()]) * numberOfPizza);
	}
}

Just a note: You don´t have to supply the Types for the Hashmap twice. Have a look at: http://openbook.galileocomputing.de/javainsel/javainsel_09_001.html#dodtp511af877-15c3-4be2-954f-b72ce7e1d666 ;)

And the types better would be an enum.