optional_datetime_format2.java

    LocalDate expectDate = LocalDate.of(2018,9,10);
    DateTimeFormatter dateTimeFormatter = new DateTimeFormatterBuilder()
      .appendOptional(DateTimeFormatter.ofPattern("yyyy M d"))
      .appendOptional(DateTimeFormatter.ofPattern("d M yyyy"))
      .appendOptional(DateTimeFormatter.ofPattern("d.M.yyyy"))
      .appendOptional(DateTimeFormatter.ofPattern("d/M/yyyy"))
      .toFormatter();
    assertThat(LocalDate.parse("2018 09 10",dateTimeFormatter)).isEqualTo(expectDate);
    assertThat(LocalDate.parse("10 9 2018",dateTimeFormatter)).isEqualTo(expectDate);
    assertThat(LocalDate.parse("10.09.2018",dateTimeFormatter)).isEqualTo(expectDate);
    assertThat(LocalDate.parse("10/9/2018",dateTimeFormatter)).isEqualTo(expectDate);