MergeAndFlatMapExample.java

package com.kiroule.ocpupgradejava8.topic6_3;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.stream.Collectors;
import java.util.stream.Stream;

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

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

    List<String> phrases = Arrays.asList(
        "sporadic perjury",
        "confounded skimming",
        "incumbent jailer",
        "confounded jailer");

    List<String> uniqueWords = phrases
        .stream()
        .flatMap(phrase -> Stream.of(phrase.split(" +")))
        .distinct()
        .sorted()
        .collect(Collectors.toList());
    System.out.println("Unique words: " + uniqueWords);

    Map<Integer, String> lengthToWordsMap = new HashMap<>();
    Consumer<String> action = w -> {
      BiFunction<String, String, String>
          remappingFunction =
          (value, newValue) -> value + ", " + newValue;
      lengthToWordsMap.merge(w.length(), w, remappingFunction);
    };
    uniqueWords.forEach(action);

    lengthToWordsMap
        .forEach((key, value) -> System.out.printf("%nWords with length %d: %s", key, value));
  }
}