update partitioning examples

Author: mariofusco

src/main/java/lambdasinaction/chap10/BestPriceFinderMain.java

@@ -11,10 +11,10 @@ public class BestPriceFinderMain {
     private static BestPriceFinder bestPriceFinder = new BestPriceFinder();
 
     public static void main(String[] args) {
-        execute("sequential", () -> bestPriceFinder.findPriceSequential("myPhone"));
-        execute("parallel", () -> bestPriceFinder.findPriceParallel("myPhone"));
+        //execute("sequential", () -> bestPriceFinder.findPriceSequential("myPhone"));
+        //execute("parallel", () -> bestPriceFinder.findPriceParallel("myPhone"));
         execute("composed CompletableFuture", () -> bestPriceFinder.findPrice("myPhone"));
-        bestPriceFinder.printPricesStream();
+        //bestPriceFinder.printPricesStream();
     }
 
     private static void execute(String msg, Supplier<List<String>> s) {

src/main/java/lambdasinaction/chap10/Util.java

@@ -11,8 +11,8 @@ public class Util {
     private static final DecimalFormat formatter = new DecimalFormat("#.##", new DecimalFormatSymbols(Locale.US));
 
     public static void delay() {
-        //int delay = 1000;
-        int delay = 500 + RANDOM.nextInt(2000);
+        int delay = 1000;
+        //int delay = 500 + RANDOM.nextInt(2000);
         try {
             Thread.sleep(delay);
         } catch (InterruptedException e) {

src/main/java/lambdasinaction/chap5/CollectorHarness.java

@@ -7,7 +7,7 @@
 public class CollectorHarness {
 
     public static void main(String[] args) {
-        System.out.println("Partitioning done in: " + execute(PartitionPrimeNumbers::partitionPrimes) + " msecs");
+        //System.out.println("Partitioning done in: " + execute(PartitionPrimeNumbers::partitionPrimes) + " msecs");
         System.out.println("Partitioning done in: " + execute(PartitionPrimeNumbers::partitionPrimesWithCustomCollector) + " msecs" );
     }
 
@@ -18,6 +18,7 @@ private static long execute(Consumer<Integer> primePartitioner) {
             primePartitioner.accept(1_000_000);
             long duration = (System.nanoTime() - start) / 1_000_000;
             if (duration < fastest) fastest = duration;
+            System.out.println("done in " + duration);
         }
         return fastest;
     }

src/main/java/lambdasinaction/chap5/PartitionPrimeNumbers.java

@@ -17,23 +17,24 @@ public static void main(String ... args) {
     }
 
     public static Map<Boolean, List<Integer>> partitionPrimes(int n) {
-        return Stream.iterate(2, i -> i + 1).limit(n-1)
+        return IntStream.rangeClosed(2, n).boxed()
                 .collect(partitioningBy(candidate -> isPrime(candidate)));
     }
 
     public static boolean isPrime(int candidate) {
-        return Stream.iterate(2, i -> i + 1)
+        return IntStream.rangeClosed(2, candidate-1)
                 .limit((long) Math.floor(Math.sqrt((double) candidate)) - 1)
                 .noneMatch(i -> candidate % i == 0);
     }
 
     public static Map<Boolean, List<Integer>> partitionPrimesWithCustomCollector(int n) {
-        return Stream.iterate(2, i -> i + 1).limit(n-1).collect(new PrimeNumbersCollector());
+        return IntStream.rangeClosed(2, n).boxed().collect(new PrimeNumbersCollector());
     }
 
     public static boolean isPrime(List<Integer> primes, Integer candidate) {
         double candidateRoot = Math.sqrt((double) candidate);
-        return takeWhile(primes, i -> i <= candidateRoot).stream().noneMatch(i -> candidate % i == 0);
+        return primes.stream().filter(p -> p < candidateRoot).noneMatch(p -> candidate % p == 0);
+        //return takeWhile(primes, i -> i <= candidateRoot).stream().noneMatch(i -> candidate % i == 0);
     }
 
     public static <A> List<A> takeWhile(List<A> list, Predicate<A> p) {

src/main/java/lambdasinaction/chap5/Partitioning.java

@@ -4,6 +4,7 @@
 import java.util.function.*;
 import java.util.stream.*;
 
+import static java.util.Comparator.comparingInt;
 import static java.util.stream.Collectors.*;
 import static lambdasinaction.chap5.Dish.menu;
 
@@ -27,7 +28,7 @@ private static Object mostCaloricPartitionedByVegetarian() {
         return menu.stream().collect(
                 partitioningBy(Dish::isVegetarian,
                         collectingAndThen(
-                                reducing((d1, d2) -> d1.getCalories() > d2.getCalories() ? d1 : d2),
+                                maxBy(comparingInt(Dish::getCalories)),
                                 Optional::get)));
     }
 }