Decision tables: Difference between revisions

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 For large numbers of rules and few actions, J's native support of sparse arrays might provide a performance advantage, particularly in space.  A minor note about the implementation here: the verb (function) <tt>troubleshoot</tt> is generalized, and reusable on any set of rule table, questions, and suggested actions.  The default is to use those given in the printer troubleshooting table.
+=={{header|Java}}==
+{{trans|Kotlin}}
+<lang java>import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.List;
+import java.util.Objects;
+public class DecisionTables {
+    private static class Pair<T, U> {
+        private final T t;
+        private final U u;
+        public static <T, U> Pair<T, U> of(T t, U u) {
+            return new Pair<>(t, u);
+        }
+        public Pair(T t, U u) {
+            this.t = t;
+            this.u = u;
+        }
+        public T getFirst() {
+            return t;
+        }
+        public U getSecond() {
+            return u;
+        }
+    }
+    private static final List<Pair<String, String>> conditions = List.of(
+        Pair.of("Printer prints", "NNNNYYYY"),
+        Pair.of("A red light is flashing", "YYNNYYNN"),
+        Pair.of("Printer is recognized by computer", "NYNYNYNY")
+    );
+    private static final List<Pair<String, String>> actions = List.of(
+        Pair.of("Check the power cable", "NNYNNNNN"),
+        Pair.of("Check the printer-computer cable", "YNYNNNNN"),
+        Pair.of("Ensure printer software is installed", "YNYNYNYN"),
+        Pair.of("Check/replace ink", "YYNNNYNN"),
+        Pair.of("Check for paper jam", "NYNYNNNN")
+    );
+    public static void main(String[] args) throws IOException {
+        final int nc = conditions.size();
+        final int na = actions.size();
+        final int nr = conditions.get(0).getSecond().length();
+        final int np = 7;
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        System.out.println("Please answer the following questions with a y or n:");
+        final boolean[] answers = new boolean[nc];
+        for (int c = 0; c < nc; ++c) {
+            String input;
+            do {
+                System.out.printf("  %s ? ", conditions.get(c).getFirst());
+                input = br.readLine().toUpperCase();
+            } while (!Objects.equals(input, "Y") && !Objects.equals(input, "N"));
+            answers[c] = Objects.equals(input, "Y");
+        }
+        System.out.println("\nRecommended action(s)");
+        outer:
+        for (int r = 0; r < nr; ++r) {
+            for (int c = 0; c < nc; ++c) {
+                char yn = answers[c] ? 'Y' : 'N';
+                if (conditions.get(c).getSecond().charAt(r) != yn) {
+                    continue outer;
+                }
+            }
+            if (r == np) {
+                System.out.println("  None (no problem detected)");
+            } else {
+                for (Pair<String, String> action : actions) {
+                    if (action.getSecond().charAt(r) == 'Y') {
+                        System.out.printf("  %s\n", action.getFirst());
+                    }
+                }
+            }
+            break;
+        }
+    }
+}</lang>
+{{out}}
+<pre>Please answer the following questions with a y or n:
+  Printer prints ? n
+  A red light is flashing ? n
+  Printer is recognized by computer ? n
+Recommended action(s)
+  Check the power cable
+  Check the printer-computer cable
+  Ensure printer software is installed</pre>
 =={{header|JavaScript}}==