59 lines
1.8 KiB
Java
59 lines
1.8 KiB
Java
// typeinfo/PetCount3.java
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// (c)2016 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
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extends LinkedHashMap<Class<? extends Pet>, Integer> {
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public 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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for(Map.Entry<Class<? extends Pet>, Integer>
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pair : entrySet())
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if(pair.getKey().isInstance(pet))
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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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StringBuilder result = new StringBuilder("{");
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for(Map.Entry<Class<? extends Pet>, Integer>
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pair : entrySet()) {
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result.append(pair.getKey().getSimpleName());
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result.append("=");
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result.append(pair.getValue());
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result.append(", ");
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}
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result.delete(result.length() - 2, result.length());
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result.append("}");
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return result.toString();
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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 Pug
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Mouse Cymric
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{Hamster=1, Rodent=5, Mouse=2, Dog=6, Cymric=5, Manx=7,
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Rat=2, Pug=3, Mutt=3, Pet=20, EgyptianMau=2, Cat=9}
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*/
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