OnJava8-Examples/typeinfo/PetCount3.java
Bruce Eckel bc0026c3e1 Radically reorganized
Plus many new examples in "streams" chapter.
2015-11-11 20:20:04 -08:00

52 lines
1.5 KiB
Java

// typeinfo/PetCount3.java
// Using isInstance()
import typeinfo.pets.*;
import java.util.*;
import onjava.*;
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);
}
@Override
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.print(pet.getClass().getSimpleName() + " ");
petCount.count(pet);
}
System.out.println();
System.out.println(petCount);
}
}
/* Output:
Rat Manx Cymric Mutt Pug Cymric Pug Manx Cymric Rat
EgyptianMau Hamster EgyptianMau Mutt Mutt Cymric Mouse Pug
Mouse Cymric
{Pet=20, Dog=6, Cat=9, Rodent=5, Mutt=3, Pug=3,
EgyptianMau=2, Manx=7, Cymric=5, Rat=2, Mouse=2, Hamster=1}
*/