OnJava8-Examples/enums/RoShamBo1.java

// enums/RoShamBo1.java
// (c)2020 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.
// Demonstration of multiple dispatching
// {java enums.RoShamBo1}
package enums;
import java.util.*;
import static enums.Outcome.*;

interface Item {
  Outcome compete(Item it);
  Outcome eval(Paper p);
  Outcome eval(Scissors s);
  Outcome eval(Rock r);
}

class Paper implements Item {
  @Override
  public Outcome compete(Item it) {
    return it.eval(this);
  }
  @Override
  public Outcome eval(Paper p) { return DRAW; }
  @Override
  public Outcome eval(Scissors s) { return WIN; }
  @Override
  public Outcome eval(Rock r) { return LOSE; }
  @Override
  public String toString() { return "Paper"; }
}

class Scissors implements Item {
  @Override
  public Outcome compete(Item it) {
    return it.eval(this);
  }
  @Override
  public Outcome eval(Paper p) { return LOSE; }
  @Override
  public Outcome eval(Scissors s) { return DRAW; }
  @Override
  public Outcome eval(Rock r) { return WIN; }
  @Override
  public String toString() { return "Scissors"; }
}

class Rock implements Item {
  @Override
  public Outcome compete(Item it) {
    return it.eval(this);
  }
  @Override
  public Outcome eval(Paper p) { return WIN; }
  @Override
  public Outcome eval(Scissors s) { return LOSE; }
  @Override
  public Outcome eval(Rock r) { return DRAW; }
  @Override
  public String toString() { return "Rock"; }
}

public class RoShamBo1 {
  static final int SIZE = 20;
  private static Random rand = new Random(47);
  public static Item newItem() {
    switch(rand.nextInt(3)) {
      default:
      case 0: return new Scissors();
      case 1: return new Paper();
      case 2: return new Rock();
    }
  }
  public static void match(Item a, Item b) {
    System.out.println(
      a + " vs. " + b + ": " +  a.compete(b));
  }
  public static void main(String[] args) {
    for(int i = 0; i < SIZE; i++)
      match(newItem(), newItem());
  }
}
/* Output:
Rock vs. Rock: DRAW
Paper vs. Rock: WIN
Paper vs. Rock: WIN
Paper vs. Rock: WIN
Scissors vs. Paper: WIN
Scissors vs. Scissors: DRAW
Scissors vs. Paper: WIN
Rock vs. Paper: LOSE
Paper vs. Paper: DRAW
Rock vs. Paper: LOSE
Paper vs. Scissors: LOSE
Paper vs. Scissors: LOSE
Rock vs. Scissors: WIN
Rock vs. Paper: LOSE
Paper vs. Rock: WIN
Scissors vs. Paper: WIN
Paper vs. Scissors: LOSE
Paper vs. Scissors: LOSE
Paper vs. Scissors: LOSE
Paper vs. Scissors: LOSE
*/