Technical proofing by Jean-Francois Morin

jeffmorin · jeffmorin · commit 73251635d40b · 2014-06-28T21:57:52.000-04:00
diff --git a/src/main/java/lambdasinaction/chap10/ExchangeService.java b/src/main/java/lambdasinaction/chap10/ExchangeService.java
@@ -0,0 +1,26 @@
+package lambdasinaction.chap10;
+
+import static lambdasinaction.chap10.Util.delay;
+
+public class ExchangeService {
+
+    public enum Money {
+        USD(1.0), EUR(1.35387), GBP(1.69715), CAD(.92106), MXN(.07683);
+
+        private final double rate;
+
+        Money(double rate) {
+            this.rate = rate;
+        }
+    }
+
+    public static double getRate(Money source, Money destination) {
+        return getRateWithDelay(source, destination);
+    }
+
+    private static double getRateWithDelay(Money source, Money destination) {
+        delay();
+        return destination.rate / source.rate;
+    }
+
+}
diff --git a/src/main/java/lambdasinaction/chap13/PersistentTrainJourney.java b/src/main/java/lambdasinaction/chap13/PersistentTrainJourney.java
@@ -0,0 +1,66 @@
+package lambdasinaction.chap13;
+
+import java.util.function.Consumer;
+
+public class PersistentTrainJourney {
+
+    public static void main(String[] args) {
+        TrainJourney tj1 = new TrainJourney(40, new TrainJourney(30, null));
+        TrainJourney tj2 = new TrainJourney(20, new TrainJourney(50, null));
+
+        TrainJourney appended = append(tj1, tj2);
+        visit(appended, tj -> { System.out.print(tj.price + " - "); });
+        System.out.println();
+
+        // A new TrainJourney is created without altering tj1 and tj2.
+        TrainJourney appended2 = append(tj1, tj2);
+        visit(appended2, tj -> { System.out.print(tj.price + " - "); });
+        System.out.println();
+
+        // tj1 is altered but it's still not visible in the results.
+        TrainJourney linked = link(tj1, tj2);
+        visit(linked, tj -> { System.out.print(tj.price + " - "); });
+        System.out.println();
+
+        // ... but here, if this code is uncommented, tj2 will be appended
+        // at the end of the already altered tj1. This will cause a
+        // StackOverflowError from the endless visit() recursive calls on
+        // the tj2 part of the twice altered tj1.
+        /*TrainJourney linked2 = link(tj1, tj2);
+        visit(linked2, tj -> { System.out.print(tj.price + " - "); });
+        System.out.println();*/
+    }
+
+    static class TrainJourney {
+        public int price;
+        public TrainJourney onward;
+
+        public TrainJourney(int p, TrainJourney t) {
+            price = p;
+            onward = t;
+        }
+    }
+
+    static TrainJourney link(TrainJourney a, TrainJourney b) {
+        if (a == null) {
+            return b;
+        }
+        TrainJourney t = a;
+        while (t.onward != null) {
+            t = t.onward;
+        }
+        t.onward = b;
+        return a;
+    }
+
+    static TrainJourney append(TrainJourney a, TrainJourney b) {
+        return a == null ? b : new TrainJourney(a.price, append(a.onward, b));
+    }
+
+    static void visit(TrainJourney journey, Consumer<TrainJourney> c) {
+        if (journey != null) {
+            c.accept(journey);
+            visit(journey.onward, c);
+        }
+    }
+}
diff --git a/src/main/java/lambdasinaction/chap13/PersistentTree.java b/src/main/java/lambdasinaction/chap13/PersistentTree.java
@@ -0,0 +1,82 @@
+package lambdasinaction.chap13;
+
+public class PersistentTree {
+
+    public static void main(String[] args) {
+        Tree t = new Tree("Mary", 22,
+                new Tree("Emily", 20,
+                        new Tree("Alan", 50, null, null),
+                        new Tree("Georgie", 23, null, null)
+                ),
+                new Tree("Tian", 29,
+                        new Tree("Raoul", 23, null, null),
+                        null
+                )
+        );
+
+        // found = 23
+        System.out.println(lookup("Raoul", -1, t));
+        // not found = -1
+        System.out.println(lookup("Jeff", -1, t));
+
+        Tree f = fupdate("Jeff", 80, t);
+        // found = 80
+        System.out.println(lookup("Jeff", -1, f));
+
+        Tree u = update("Jim", 40, t);
+        // t was not altered by fupdate, so Jeff is not found = -1
+        System.out.println(lookup("Jeff", -1, u));
+        // found = 40
+        System.out.println(lookup("Jim", -1, u));
+
+        Tree f2 = fupdate("Jeff", 80, t);
+        // found = 80
+        System.out.println(lookup("Jeff", -1, f2));
+        // f2 built from t altered by update() above, so Jim is still present = 40
+        System.out.println(lookup("Jim", -1, f2));
+    }
+
+    static class Tree {
+        private String key;
+        private int val;
+        private Tree left, right;
+
+        public Tree(String k, int v, Tree l, Tree r) {
+            key = k;
+            val = v;
+            left = l;
+            right = r;
+        }
+    }
+
+    public static int lookup(String k, int defaultval, Tree t) {
+        if (t == null)
+            return defaultval;
+        if (k.equals(t.key))
+            return t.val;
+        return lookup(k, defaultval, k.compareTo(t.key) < 0 ? t.left : t.right);
+    }
+
+    public static Tree update(String k, int newval, Tree t) {
+        if (t == null)
+            t = new Tree(k, newval, null, null);
+        else if (k.equals(t.key))
+            t.val = newval;
+        else if (k.compareTo(t.key) < 0)
+            t.left = update(k, newval, t.left);
+        else
+            t.right = update(k, newval, t.right);
+        return t;
+    }
+
+    public static Tree fupdate(String k, int newval, Tree t) {
+        return (t == null) ?
+            new Tree(k, newval, null, null) :
+             k.equals(t.key) ?
+               new Tree(k, newval, t.left, t.right) :
+          k.compareTo(t.key) < 0 ?
+            new Tree(t.key, t.val, fupdate(k,newval, t.left), t.right) :
+            new Tree(t.key, t.val, t.left, fupdate(k,newval, t.right));
+   }
+
+}
