PredicateInterfaceExample.java

package com.kiroule.ocpupgradejava8.topic2_6;

import java.util.Arrays;
import java.util.List;
import java.util.function.Consumer;
import java.util.function.Predicate;

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

  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("John", "Zoidberg", "alien"));

    System.out.println("Robots:");
    printCharactersBySpecies(characters, c -> {
      System.out.printf("Evaluating character's species[%s] %n", c.getSpecies());
      return c.getSpecies().equals("robot");
    });

    System.out.println("\nMutants:");
    printCharactersBySpecies(characters, new MutantSpeciesPredicate());

    System.out.println("\nHumans:");
    printCharactersBySpecies(characters, c -> c.getSpecies().equals("human"),
                             c -> System.out
                                 .println(c.getFirstName() + " " + c.getLastName().toUpperCase()));

    System.out.println("\nAliens:");
    printCharactersBySpecies(characters, FuturamaCharacter::isAlienSpecies);
  }

  public static void printCharactersBySpecies(List<FuturamaCharacter> characters,
                                              Predicate<FuturamaCharacter> predicate) {
    characters.stream()
        .filter(predicate::test)
        .forEach(c -> System.out.println(c.getFirstName() + " " + c.getLastName()));
  }

  public static void printCharactersBySpecies(List<FuturamaCharacter> characters,
                                              Predicate<FuturamaCharacter> predicate,
                                              Consumer<FuturamaCharacter> consumer) {
    characters.stream()
        .filter(predicate::test)
        .forEach(consumer::accept);
  }
}

class MutantSpeciesPredicate implements Predicate<FuturamaCharacter> {

  @Override
  public boolean test(FuturamaCharacter character) {
    return character.getSpecies().equals("mutant");
  }
}

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 boolean isAlienSpecies() {
    return "alien".equals(species);
  }

  public String getFirstName() {
    return firstName;
  }

  public String getLastName() {
    return lastName;
  }

  public String getSpecies() {
    return species;
  }
}