136 lines
2.9 KiB
Java
136 lines
2.9 KiB
Java
// patterns/PaperScissorsRock.java
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// (c)2020 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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// Demonstration of multiple dispatching
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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import onjava.*;
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import static onjava.Tuple.*;
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enum Outcome { WIN, LOSE, DRAW }
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interface Item {
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Outcome compete(Item it);
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Outcome eval(Paper p);
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Outcome eval(Scissors s);
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Outcome eval(Rock r);
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}
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class Paper implements Item {
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@Override
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public Outcome compete(Item it) {
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return it.eval(this);
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}
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@Override
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public Outcome eval(Paper p) {
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return Outcome.DRAW;
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}
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@Override
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public Outcome eval(Scissors s) {
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return Outcome.WIN;
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}
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@Override
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public Outcome eval(Rock r) {
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return Outcome.LOSE;
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}
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@Override
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public String toString() { return "Paper"; }
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}
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class Scissors implements Item {
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@Override
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public Outcome compete(Item it) {
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return it.eval(this);
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}
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@Override
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public Outcome eval(Paper p) {
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return Outcome.LOSE;
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}
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@Override
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public Outcome eval(Scissors s) {
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return Outcome.DRAW;
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}
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@Override
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public Outcome eval(Rock r) {
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return Outcome.WIN;
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}
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@Override
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public String toString() { return "Scissors"; }
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}
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class Rock implements Item {
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@Override
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public Outcome compete(Item it) {
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return it.eval(this);
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}
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@Override
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public Outcome eval(Paper p) {
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return Outcome.WIN;
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}
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@Override
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public Outcome eval(Scissors s) {
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return Outcome.LOSE;
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}
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@Override
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public Outcome eval(Rock r) {
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return Outcome.DRAW;
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}
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@Override
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public String toString() { return "Rock"; }
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}
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class ItemFactory {
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static List<Supplier<Item>> items =
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Arrays.asList(
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Scissors::new, Paper::new, Rock::new);
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static final int SZ = items.size();
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private static SplittableRandom rand =
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new SplittableRandom(47);
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public static Item newItem() {
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return items.get(rand.nextInt(SZ)).get();
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}
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public static Tuple2<Item,Item> newPair() {
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return tuple(newItem(), newItem());
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}
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}
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class Compete {
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public static Outcome match(Tuple2<Item,Item> p) {
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System.out.print(p.a1 + " -> " + p.a2 + " : ");
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return p.a1.compete(p.a2);
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}
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}
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public class PaperScissorsRock {
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public static void main(String[] args) {
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Stream.generate(ItemFactory::newPair)
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.limit(20)
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.map(Compete::match)
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.forEach(System.out::println);
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}
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}
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/* Output:
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Scissors -> Rock : LOSE
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Scissors -> Paper : WIN
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Rock -> Paper : LOSE
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Rock -> Rock : DRAW
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Rock -> Paper : LOSE
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Paper -> Scissors : LOSE
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Rock -> Paper : LOSE
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Scissors -> Scissors : DRAW
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Scissors -> Rock : LOSE
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Scissors -> Paper : WIN
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Scissors -> Rock : LOSE
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Paper -> Scissors : LOSE
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Rock -> Rock : DRAW
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Scissors -> Scissors : DRAW
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Paper -> Paper : DRAW
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Scissors -> Paper : WIN
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Scissors -> Rock : LOSE
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Scissors -> Paper : WIN
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Rock -> Paper : LOSE
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Rock -> Scissors : WIN
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*/
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