DocumentType first pass in enum refactoring demo

DocumentType.java

public enum DocumentType {
  TXT("txt", "text"),
  MD("md", "markdown"),
  HTML("html", "htm");

  String[] extensions;

  DocumentType(String... extensions) {
    this.extensions = Arrays.copyOf(extensions, extensions.length);
  }

  public static DocumentType forPath(Path file) {
    String ext = FileNameHelper.getLowercaseExtension(file);
    for (DocumentType type : DocumentType.values()) {
      if (Arrays.stream(type.extensions).anyMatch(ext::equals)) {
        return type;
      }
    }
    return null;
  }
}