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PetCount3.java
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53 lines (52 loc) · 1.61 KB
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// typeinfo/PetCount3.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Using isInstance()
import java.util.*;
import java.util.stream.*;
import onjava.*;
import typeinfo.pets.*;
public class PetCount3 {
static class Counter extends
LinkedHashMap<Class<? extends Pet>, Integer> {
Counter() {
super(LiteralPetCreator.ALL_TYPES.stream()
.map(lpc -> Pair.make(lpc, 0))
.collect(
Collectors.toMap(Pair::key, Pair::value)));
}
public void count(Pet pet) {
// Class.isInstance() eliminates instanceofs:
entrySet().stream()
.filter(pair -> pair.getKey().isInstance(pet))
.forEach(pair ->
put(pair.getKey(), pair.getValue() + 1));
}
@Override
public String toString() {
String result = entrySet().stream()
.map(pair -> String.format("%s=%s",
pair.getKey().getSimpleName(),
pair.getValue()))
.collect(Collectors.joining(", "));
return "{" + result + "}";
}
}
public static void main(String[] args) {
Counter petCount = new Counter();
Pets.stream()
.limit(20)
.peek(petCount::count)
.forEach(p -> System.out.print(
p.getClass().getSimpleName() + " "));
System.out.println("\n" + petCount);
}
}
/* Output:
Rat Manx Cymric Mutt Pug Cymric Pug Manx Cymric Rat
EgyptianMau Hamster EgyptianMau Mutt Mutt Cymric Mouse
Pug Mouse Cymric
{Rat=2, Pug=3, Mutt=3, Mouse=2, Cat=9, Dog=6, Cymric=5,
EgyptianMau=2, Rodent=5, Hamster=1, Manx=7, Pet=20}
*/