PetCount3.java

//: typeinfo/PetCount3.java
// Using isInstance()

package thinkinginjava.typeinfo;

import java.util.LinkedHashMap;
import java.util.Map;

import thinkinginjava.typeinfo.pets.LiteralPetCreator;
import thinkinginjava.typeinfo.pets.Pet;
import thinkinginjava.typeinfo.pets.Pets;

public class PetCount3 {
	static class PetCounter extends
			LinkedHashMap<Class<? extends Pet>, Integer> {
		public PetCounter() {
			super(MapData.map(LiteralPetCreator.allTypes, 0));
		}

		public void count(Pet pet) {
			// Class.isInstance() eliminates instanceofs:
			for (Map.Entry<Class<? extends Pet>, Integer> pair : entrySet())
				if (pair.getKey().isInstance(pet))
					put(pair.getKey(), pair.getValue() + 1);
		}

		public String toString() {
			StringBuilder result = new StringBuilder("{");
			for (Map.Entry<Class<? extends Pet>, Integer> pair : entrySet()) {
				result.append(pair.getKey().getSimpleName());
				result.append("=");
				result.append(pair.getValue());
				result.append(", ");
			}
			result.delete(result.length() - 2, result.length());
			result.append("}");
			return result.toString();
		}
	}

	public static void main(String[] args) {
		PetCounter petCount = new PetCounter();
		for (Pet pet : Pets.createArray(20)) {
			System.out.println((pet.getClass().getSimpleName() + " "));
			petCount.count(pet); 
		}
		System.out.println();
		System.out.println(petCount);
	}
}