(feat) Lab 6 exercise 9 - Rock Paper Scissors (no input version)

week1.java

@@ -1,4 +1,5 @@
 import java.util.Calendar;
+import java.util.Random;
 import java.util.Scanner;
 import java.util.concurrent.ThreadLocalRandom;
 
@@ -7,7 +8,7 @@ class runLabs {
         new Lab4();
         new Lab5();
         new Lab6();
-        new Lab7();
+        // new Lab7();
     }
 }
 
@@ -369,7 +370,7 @@ class Lab6 extends Lab {
          * @param padChar Character to pad with
          * @return The padded result
          */
-        public String stringLPad(String toPad, int paddedLength, char padChar) {
+        public static String stringLPad(String toPad, int paddedLength, char padChar) {
             // early out - return unmodified
             if (toPad.length() >= paddedLength) {
                 return toPad;
@@ -387,11 +388,78 @@ class Lab6 extends Lab {
     }
 
     class six9 extends Exercise {
+        private Random random = new Random(); // initialise once
+        // see https://stackoverflow.com/a/35277291, to pick a random member of an enum, first convert it to an array
+        private Throw[] throwsArray = Throw.values(); // can't call it 'throws' for obvious reasons
+
+        final Throw randomThrow() {
+            return throwsArray[random.nextInt(throwsArray.length)];
+        }
+
         public six9() {
             super(9);
-            System.out.println(String.format("TODO: ro sham bo once we have stdin working"));
+            System.out.println(String.format("TODO: Take input when we have stdin working"));
+            Throw player1 = Throw.ROCK; // "Good ol' rock, nothing beats that"
+            Throw player2 = randomThrow();
+            playRockPaperScissors(player1, player2);
+            player2 = randomThrow();
+            playRockPaperScissors(player1, player2);
+            player2 = randomThrow();
+            playRockPaperScissors(player1, player2);
+        }
+    }
+
+    public void playRockPaperScissors (Throw player1, Throw player2) {
+        // slight semantic overload with throwing an error but I think that's the term
+        // for plays in RPS
+        String result;
+        // early out - TOASK why this doesn't work when it works in a REPL!!
+        if (player1 == player2) {
+            result = "a draw";
+        } else {
+            switch (player1) {
+                case ROCK:
+                    if (player2 == Throw.SCISSORS) { result = "R>S Player 1 wins"; }
+                    else { result = "R<P Player 2 wins"; }  // must be paper
+                    break;
+                case PAPER:
+                    if (player2 == Throw.SCISSORS) { result = "P<S Player 2 wins"; }
+                    else { result = "P>R Player 1 wins"; } // must be rock
+                    break;
+                case SCISSORS:
+                    if (player2 == Throw.ROCK) { result = "S<R Player 2 wins"; }
+                    else { result = "S>P Player 1 wins"; }  // must be paper
+                    break;
+                default:
+                    result = "undefined behaviour";
+                    break;
+                }
         }
+        writeRPSPlay(player1, player2, result);
     }
+
+    public String getThrowName(Throw thrown) {
+        // This could probably be done in the enum itself
+        switch (thrown) {
+        case ROCK: return six8.stringLPad("rock", 8, ' '); // pad to 'scissors' length so everything stays lined-up
+        case PAPER: return six8.stringLPad("paper", 8, ' ');
+        case SCISSORS: return "scissors";
+        default: return "uh?";
+        }
+    }
+
+    public void writeRPSPlay (Throw player1, Throw player2, String result) {
+        System.out.printf("Player 1 throws... %s\t\t", getThrowName(player1));
+        System.out.printf("Player 2 throws... %s\t\t", getThrowName(player2));
+        System.out.println(String.format("The result is...\t%s", result));
+    }
+
+    enum Throw {
+        ROCK,
+        PAPER,
+        SCISSORS
+    }
+
     /* TOASK - is there a better way of returning multiple values in Java?
        à la python, ie: return (quotient, remainder)
     */