CollectionImprovementsExample.java

package com.kiroule.ocpupgradejava8.topic6_1;

import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

import static com.kiroule.ocpupgradejava8.topic6_1.Species.HUMAN;
import static com.kiroule.ocpupgradejava8.topic6_1.Species.MUTANT;
import static com.kiroule.ocpupgradejava8.topic6_1.Species.ROBOT;

/**
 * @author Igor Baiborodine
 */
public class CollectionImprovementsExample {

  public static void main(String... args) {

    List<FuturamaCharacter> characters = new LinkedList<>(Arrays.asList(
        new FuturamaCharacter("Bender", "Rodriguez", 5, ROBOT),
        new FuturamaCharacter("Philip", "Fry", 126, HUMAN),
        new FuturamaCharacter("Turanga", "Leela", 22, MUTANT),
        new FuturamaCharacter("Hubert", "Farnsworth", 161, HUMAN)));

    System.out.println("Futurama characters:");
    characters.forEach(System.out::println);

    // Map.forEach
    Map<Species, List<FuturamaCharacter>> speciesToFuturamaCharactersMap = characters
        .stream()
        .collect(Collectors.groupingBy(FuturamaCharacter::getSpecies));
    System.out.println("\nCharacters by species: ");
    speciesToFuturamaCharactersMap.forEach((k, v) -> System.out.println(k + ": " + v));

    // List.removeIf
    System.out.println("\nHumans: ");
    characters.removeIf(c -> !c.getSpecies().equals(Species.HUMAN));
    characters.forEach(System.out::println);

    // List.replaceAll
    List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
    numbers.replaceAll(x -> x % 2 == 0 ? x : 0);
    System.out.println("\nOdd numbers replaced by zero: " + numbers);

    // Map.computeIfAbsent
    class Fibonacci {

      private Map<Integer, Integer> cache = new ConcurrentHashMap<>();

      public int get(int n) {
        if (n == 0 || n == 1) {
          return n;
        }
        return cache.computeIfAbsent(n, key -> get(n - 2) + get(n - 1));
      }
    }
    Fibonacci fibonacci = new Fibonacci();
    System.out.print("\nFirst 10 Fibonacci numbers: ");
    IntStream.range(0, 10).forEach(x -> System.out.print(fibonacci.get(x) + " "));
  }
}

enum Species {
  HUMAN, ROBOT, MUTANT
}

class FuturamaCharacter {

  private String firstName;
  private String lastName;
  private int age = 0;
  private Species species = HUMAN;

  public FuturamaCharacter(String firstName, String lastName, int age, Species species) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
    this.species = species;
  }

  public String getFirstName() {
    return firstName;
  }

  public String getLastName() {
    return lastName;
  }

  public Species getSpecies() {
    return species;
  }

  @Override
  public String toString() {
    return firstName + " " + lastName + " [" + age + "][" + species + "]";
  }
}