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