StreamInterfaceExample.java

package com.kiroule.ocpupgradejava8.topic3_2;

import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Stream;

import static java.lang.String.format;

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

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

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

    Stream<FuturamaCharacter> characterStream = characters.stream();

    long count = characterStream
        .peek(c -> System.out.println("Filtered value: " + c))
        .filter(new MutantSpeciesPredicate())
        .count();
    System.out.printf("%nFound %d mutant(s).", count);

    Thread.sleep(500);
    // Cannot re-use the stream, it will throw a runtime exception:
    // java.lang.IllegalStateException: stream has already been operated upon or closed
    characterStream.count();
  }
}

class MutantSpeciesPredicate implements Predicate<FuturamaCharacter> {

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

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);
  }
}