joiner.java

  // instead of
  public String legacyJoin(String... args) {
    return java.util.Arrays
      .stream(args)
      .collect(Collectors.joining(", "));
  }

  // do it the functional way
  public String vavrJoin(String... args) {
    return io.vavr.collection.List
      .of(args)
      .mkString(", ");
  }

  // or just be aware of what the JDK offers
  public String stringJavaJoiner(String... args) {
    return String.join(", ", args);
  }