OnJava8-Examples/reflection/PetCounter3.java at master · CSapprenticeWT/OnJava8-Examples · GitHub

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// reflection/PetCounter3.java

// 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 reflection.pets.*;

public class PetCounter3 {

static class Counter extends

HashMap<Class<? extends Pet>, Integer> {

Counter() {

super(PetCreator.ALL_TYPES.stream()

.map(type -> Pair.make(type, 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();

new PetCreator().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

{EgyptianMau=2, Mouse=2, Pet=20, Cymric=5, Rat=2,

Dog=6, Mutt=3, Hamster=1, Cat=9, Manx=7, Rodent=5,

Pug=3}

OnJava8-Examples/reflection/PetCounter3.java at master · CSapprenticeWT/OnJava8-Examples · GitHub

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