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mariofuscomariofusco
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add code for chapter 5
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‎src/main/java/lambdasinaction/chap5/CollectorHarness.java‎

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package lambdasinaction.chap5;
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import java.util.function.*;
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import static lambdasinaction.chap5.PartitionPrimeNumbers.*;
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public class CollectorHarness {
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public static void main(String[] args) {
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System.out.println("Partitioning done in: " + execute(PartitionPrimeNumbers::partitionPrimes) + " msecs");
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System.out.println("Partitioning done in: " + execute(PartitionPrimeNumbers::partitionPrimesWithCustomCollector) + " msecs" );
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}
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private static long execute(Consumer<Integer> primePartitioner) {
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long fastest = Long.MAX_VALUE;
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for (int i = 0; i < 10; i++) {
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long start = System.nanoTime();
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primePartitioner.accept(1_000_000);
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long duration = (System.nanoTime() - start) / 1_000_000;
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if (duration < fastest) fastest = duration;
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}
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return fastest;
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}
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}

‎src/main/java/lambdasinaction/chap5/Dish.java‎

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package lambdasinaction.chap5;
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import java.util.*;
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public class Dish {
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private final String name;
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private final boolean vegetarian;
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private final int calories;
@@ -35,4 +38,15 @@ public enum Type { MEAT, FISH, OTHER }
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public String toString() {
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return name;
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}
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public static final List<Dish> menu =
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Arrays.asList( new Dish("pork", false, 800, Dish.Type.MEAT),
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new Dish("beef", false, 700, Dish.Type.MEAT),
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new Dish("chicken", false, 400, Dish.Type.MEAT),
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new Dish("french fries", true, 530, Dish.Type.OTHER),
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new Dish("rice", true, 350, Dish.Type.OTHER),
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new Dish("season fruit", true, 120, Dish.Type.OTHER),
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new Dish("pizza", true, 550, Dish.Type.OTHER),
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new Dish("prawns", false, 400, Dish.Type.FISH),
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new Dish("salmon", false, 450, Dish.Type.FISH));
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}

‎src/main/java/lambdasinaction/chap5/Grouping.java‎

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package lambdasinaction.chap5;
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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import static java.util.stream.Collectors.*;
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import static lambdasinaction.chap5.Dish.menu;
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public class Grouping {
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enum CaloricLevel { DIET, NORMAL, FAT };
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public static void main(String ... args) {
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System.out.println("Dishes grouped by type: " + groupDishesByType());
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System.out.println("Dishes grouped by caloric level: " + groupDishesByCaloricLevel());
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System.out.println("Dishes grouped by type and caloric level: " + groupDishedByTypeAndCaloricLevel());
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System.out.println("Count dishes in groups: " + countDishesInGroups());
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System.out.println("Most caloric dishes by type: " + mostCaloricDishesByType());
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System.out.println("Most caloric dishes by type: " + mostCaloricDishesByTypeWithoutOprionals());
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System.out.println("Sum calories by type: " + sumCaloriesByType());
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System.out.println("Caloric levels by type: " + caloricLevelsByType());
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}
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private static Map<Dish.Type, List<Dish>> groupDishesByType() {
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return menu.stream().collect(groupingBy(Dish::getType));
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}
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private static Map<CaloricLevel, List<Dish>> groupDishesByCaloricLevel() {
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return menu.stream().collect(
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groupingBy(dish -> {
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if (dish.getCalories() <= 400) return CaloricLevel.DIET;
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else if (dish.getCalories() <= 700) return CaloricLevel.NORMAL;
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else return CaloricLevel.FAT;
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} ));
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}
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private static Map<Dish.Type, Map<CaloricLevel, List<Dish>>> groupDishedByTypeAndCaloricLevel() {
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return menu.stream().collect(
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groupingBy(Dish::getType,
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groupingBy(dish -> {
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if (dish.getCalories() <= 400) return CaloricLevel.DIET;
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else if (dish.getCalories() <= 700) return CaloricLevel.NORMAL;
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else return CaloricLevel.FAT;
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} )
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)
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);
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}
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private static Map<Dish.Type, Long> countDishesInGroups() {
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return menu.stream().collect(groupingBy(Dish::getType, counting()));
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}
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private static Map<Dish.Type, Optional<Dish>> mostCaloricDishesByType() {
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return menu.stream().collect(
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groupingBy(Dish::getType,
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reducing((d1, d2) -> d1.getCalories() > d2.getCalories() ? d1 : d2)));
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}
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private static Map<Dish.Type, Dish> mostCaloricDishesByTypeWithoutOprionals() {
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return menu.stream().collect(
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groupingBy(Dish::getType,
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collectingAndThen(
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reducing((d1, d2) -> d1.getCalories() > d2.getCalories() ? d1 : d2),
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Optional::get)));
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}
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private static Map<Dish.Type, Integer> sumCaloriesByType() {
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return menu.stream().collect(groupingBy(Dish::getType,
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summingInt(Dish::getCalories)));
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}
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private static Map<Dish.Type, Set<CaloricLevel>> caloricLevelsByType() {
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return menu.stream().collect(
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groupingBy(Dish::getType, mapping(
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dish -> { if (dish.getCalories() <= 400) return CaloricLevel.DIET;
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else if (dish.getCalories() <= 700) return CaloricLevel.NORMAL;
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else return CaloricLevel.FAT; },
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toSet() )));
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}
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}

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

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package lambdasinaction.chap5;
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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import static java.util.stream.Collectors.*;
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import static lambdasinaction.chap5.Dish.menu;
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import static java.util.stream.Collector.Characteristics.*;
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public class PartitionPrimeNumbers {
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public static void main(String ... args) {
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System.out.println("Numbers partitioned in prime and non-prime: " + partitionPrimes(100));
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System.out.println("Numbers partitioned in prime and non-prime: " + partitionPrimesWithCustomCollector(100));
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}
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public static Map<Boolean, List<Integer>> partitionPrimes(int n) {
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return Stream.iterate(2, i -> i + 1).limit(n)
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.collect(partitioningBy(candidate -> isPrime(candidate)));
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}
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public static boolean isPrime(int candidate) {
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return Stream.iterate(2, i -> i + 1)
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.limit((long) Math.floor(Math.sqrt((double) candidate)) - 1)
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.noneMatch(i -> candidate % i == 0);
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}
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public static Map<Boolean, List<Integer>> partitionPrimesWithCustomCollector(int n) {
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return Stream.iterate(2, i -> i + 1).limit(n).collect(new PrimeNumbersCollector());
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}
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public static boolean isPrime(List<Integer> primes, Integer candidate) {
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double candidateRoot = Math.sqrt((double) candidate);
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return takeWhile(primes, i -> i <= candidateRoot).stream().noneMatch(i -> candidate % i == 0);
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}
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public static <A> List<A> takeWhile(List<A> list, Predicate<A> p) {
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int i = 0;
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for (A item : list) {
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if (!p.test(item)) {
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return list.subList(0, i);
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}
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i++;
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}
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return list;
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}
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public static class PrimeNumbersCollector
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implements Collector<Integer, Map<Boolean, List<Integer>>, Map<Boolean, List<Integer>>> {
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@Override
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public Supplier<Map<Boolean, List<Integer>>> supplier() {
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return () -> new HashMap<Boolean, List<Integer>>() {{
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put(true, new ArrayList<Integer>());
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put(false, new ArrayList<Integer>());
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}};
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}
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@Override
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public BiConsumer<Map<Boolean, List<Integer>>, Integer> accumulator() {
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return (Map<Boolean, List<Integer>> acc, Integer candidate) -> {
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acc.get( isPrime( acc.get(true),
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candidate) )
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.add(candidate);
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};
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}
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@Override
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public BinaryOperator<Map<Boolean, List<Integer>>> combiner() {
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return (Map<Boolean, List<Integer>> map1, Map<Boolean, List<Integer>> map2) -> {
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map1.get(true).addAll(map2.get(true));
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map1.get(false).addAll(map2.get(false));
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return map1;
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};
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}
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@Override
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public Function<Map<Boolean, List<Integer>>, Map<Boolean, List<Integer>>> finisher() {
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return i -> i;
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}
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@Override
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public Set<Characteristics> characteristics() {
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return Collections.unmodifiableSet(EnumSet.of(IDENTITY_FINISH));
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}
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}
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public Map<Boolean, List<Integer>> partitionPrimesWithInlineCollector(int n) {
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return Stream.iterate(2, i -> i + 1).limit(n)
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.collect(
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() -> new HashMap<Boolean, List<Integer>>() {{
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put(true, new ArrayList<Integer>());
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put(false, new ArrayList<Integer>());
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}},
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(acc, candidate) -> {
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acc.get( isPrime(acc.get(true), candidate) )
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.add(candidate);
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},
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(map1, map2) -> {
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map1.get(true).addAll(map2.get(true));
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map1.get(false).addAll(map2.get(false));
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});
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}
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}

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

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package lambdasinaction.chap5;
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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import static java.util.stream.Collectors.*;
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import static lambdasinaction.chap5.Dish.menu;
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public class Partitioning {
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public static void main(String ... args) {
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System.out.println("Dishes partitioned by vegetarian: " + partitionByVegeterian());
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System.out.println("Vegetarian Dishes by type: " + vegetarianDishesByType());
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System.out.println("Most caloric dishes by vegetarian: " + mostCaloricPartitionedByVegetarian());
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}
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private static Map<Boolean, List<Dish>> partitionByVegeterian() {
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return menu.stream().collect(partitioningBy(Dish::isVegetarian));
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}
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private static Map<Boolean, Map<Dish.Type, List<Dish>>> vegetarianDishesByType() {
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return menu.stream().collect(partitioningBy(Dish::isVegetarian, groupingBy(Dish::getType)));
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}
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private static Object mostCaloricPartitionedByVegetarian() {
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return menu.stream().collect(
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partitioningBy(Dish::isVegetarian,
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collectingAndThen(
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reducing((d1, d2) -> d1.getCalories() > d2.getCalories() ? d1 : d2),
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Optional::get)));
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}
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}
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‎src/main/java/lambdasinaction/chap5/Reducing.java‎

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package lambdasinaction.chap5;
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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import static java.util.stream.Collectors.*;
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import static lambdasinaction.chap5.Dish.menu;
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public class Reducing {
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public static void main(String ... args) {
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System.out.println("Total calories in menu: " + calculateTotalCalories());
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System.out.println("Total calories in menu: " + calculateTotalCaloriesWithMethodReference());
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System.out.println("Total calories in menu: " + calculateTotalCaloriesWithoutCollectors());
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System.out.println("Total calories in menu: " + calculateTotalCaloriesUsingSum());
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}
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private static int calculateTotalCalories() {
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return menu.stream().collect(reducing(0, Dish::getCalories, (Integer i, Integer j) -> i + j));
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}
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private static int calculateTotalCaloriesWithMethodReference() {
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return menu.stream().collect(reducing(0, Dish::getCalories, Integer::sum));
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}
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private static int calculateTotalCaloriesWithoutCollectors() {
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return menu.stream().map(Dish::getCalories).reduce(Integer::sum).get();
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}
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private static int calculateTotalCaloriesUsingSum() {
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return menu.stream().mapToInt(Dish::getCalories).sum();
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}
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}

‎src/main/java/lambdasinaction/chap5/Summarizing.java‎

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package lambdasinaction.chap5;
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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import static java.util.stream.Collectors.*;
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import static lambdasinaction.chap5.Dish.menu;
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public class Summarizing {
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public static void main(String ... args) {
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System.out.println("Nr. of dishes: " + howManyDishes());
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System.out.println("The most caloric dish is: " + findMostCaloricDish());
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System.out.println("The most caloric dish is: " + findMostCaloricDishUsingComparator());
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System.out.println("Total calories in menu: " + calculateTotalCalories());
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System.out.println("Average calories in menu: " + calculateAverageCalories());
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System.out.println("Menu statistics: " + calculateMenuStatistics());
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System.out.println("Short menu: " + getShortMenu());
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System.out.println("Short menu comma separated: " + getShortMenuCommaSeparated());
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}
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private static long howManyDishes() {
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return menu.stream().collect(counting());
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}
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private static Dish findMostCaloricDish() {
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return menu.stream().collect(reducing((d1, d2) -> d1.getCalories() > d2.getCalories() ? d1 : d2)).get();
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}
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private static Dish findMostCaloricDishUsingComparator() {
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Comparator<Dish> dishCaloriesComparator = Comparator.comparing(Dish::getCalories);
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BinaryOperator<Dish> moreCaloricOf = BinaryOperator.maxBy(dishCaloriesComparator);
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return menu.stream().collect(reducing(moreCaloricOf)).get();
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}
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private static int calculateTotalCalories() {
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return menu.stream().collect(summingInt(Dish::getCalories));
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}
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private static Double calculateAverageCalories() {
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return menu.stream().collect(averagingInt(Dish::getCalories));
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}
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private static IntSummaryStatistics calculateMenuStatistics() {
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return menu.stream().collect(summarizingInt(Dish::getCalories));
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}
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private static String getShortMenu() {
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return menu.stream().map(Dish::getName).collect(joining());
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}
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private static String getShortMenuCommaSeparated() {
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return menu.stream().map(Dish::getName).collect(joining(", "));
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}
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}

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