ExtractDataWithMapExample.java

package com.kiroule.ocpupgradejava8.topic4_1;

import java.util.Arrays;
import java.util.List;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import static java.lang.String.format;

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

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

    List<FuturamaCharacter> characters = Arrays.asList(
        new FuturamaCharacter("Bender", "Rodriguez", "robot"),
        new FuturamaCharacter("Philip", "Fry", "human"),
        new FuturamaCharacter("Turanga", "Leela", "mutant"),
        new FuturamaCharacter("Zapp", "Brannigan", "human"));

    Stream<String> speciesStream = characters.stream()
        .peek(c -> System.out.println("Filtered value: " + c))
            // <R> Stream<R> map(Function<? super T, ? extends R> mapper);
        .map(FuturamaCharacter::getSpecies) // c -> c.getSpecies()
        .peek(s -> System.out.println("Mapped value: " + s.toUpperCase()))
        .distinct()
        .sorted();
    System.out.println("Distinct Futurama character species:");
    speciesStream.forEach(System.out::println);

    IntStream hashcodeStream = characters.stream()
        // IntStream mapToInt(ToIntFunction<? super T> mapper);
        .mapToInt(FuturamaCharacter::hashCode) // c -> c.hashCode()
        .peek(hc -> System.out.println("Mapped value: " + hc))
        .sorted();
    System.out.println("\nHashcodes:");
    hashcodeStream.forEach(System.out::println);
  }
}

class FuturamaCharacter {

  private String firstName;
  private String lastName;
  private String species = "human";

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

  public String getSpecies() {
    return species;
  }

  @Override
  public String toString() {
    return format("%s %s [%s]", firstName, lastName, species);
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }

    FuturamaCharacter character = (FuturamaCharacter) o;

    if (firstName != null ? !firstName.equals(character.firstName) : character.firstName != null) {
      return false;
    }
    if (lastName != null ? !lastName.equals(character.lastName) : character.lastName != null) {
      return false;
    }
    return !(species != null ? !species.equals(character.species) : character.species != null);

  }

  @Override
  public int hashCode() {
    int result = firstName != null ? firstName.hashCode() : 0;
    result = 31 * result + (lastName != null ? lastName.hashCode() : 0);
    result = 31 * result + (species != null ? species.hashCode() : 0);
    return result;
  }
}