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10_Blackjack/java/src/Blackjack.java

@@ -8,11 +8,14 @@ public class Blackjack {
 	public static void main(String[] args) {
 		// Intuitively it might seem like the main program logic should be right
 		// here in 'main' and that we should just use System.in and System.out
-		// directly whenever we need them.  However, by externalizing the source
-		// of input/output data (and the ordering of the cards via a custom
-		// shuffle function), we can write non-interactive and deterministic
-		// tests of the code. See UserIoTest as an example.
-        try (Reader in = new InputStreamReader(System.in)) {
+		// directly whenever we need them.  However, notice that System.out and
+		// System.in are just an OutputStream and InputStream respectively. By
+		// allowing alternate streams to be specified to Game at runtime, we can
+		// write non-interactive tests of the code. See UserIoTest as an
+		// example.
+		// Likewise, by allowing an alternative "shuffle" algorithm, test code
+		// can provide a deterministic card ordering.
+		try (Reader in = new InputStreamReader(System.in)) {
 			Writer out = new OutputStreamWriter(System.out);
 			UserIo userIo = new UserIo(in, out);
 			Deck deck = new Deck(cards -> {