java - 使用 DateTimeFormatterBuilder 解析缺失日期的日期，默认为月底

Question

我需要解析各种格式的日期。其中一些缺少“日”。现在我想默认到月底。我不确定是否有直接的方法可以默认为月底

DateTimeFormatter f = new DateTimeFormatterBuilder()
        .appendPattern("MM.yyyy")
        .parseDefaulting(DAY_OF_MONTH, 1) // can we default to end of month?
        .toFormatter();

LocalDate.parse("11.2017", f)

但如果不是，我怎么知道原始日期缺少这一天(或者使用了默认值)，因此我需要使用 LocalDate.parse("11.2017", f) 手动调整它.with(TemporalAdjusters.lastDayOfMonth()).

Answer 1

DateTimeFormatter f = new DateTimeFormatterBuilder()
      .appendPattern("MM.yyyy")
      .parseDefaulting(DAY_OF_MONTH, 31) // set 31
      .toFormatter();

只需将DAY_OF_MONTH设置为31，DAY_OF_MONTH将根据rangeUnit来选择最后一天解析月份。

/**
 * The day-of-month.
 * <p>
 * This represents the concept of the day within the month.
 * In the default ISO calendar system, this has values from 1 to 31 in most months.
 * April, June, September, November have days from 1 to 30, while February has days
 * from 1 to 28, or 29 in a leap year.
 * <p>
 * Non-ISO calendar systems should implement this field using the most recognized
 * day-of-month values for users of the calendar system.
 * Normally, this is a count of days from 1 to the length of the month.
 */
DAY_OF_MONTH("DayOfMonth", DAYS, MONTHS, ValueRange.of(1, 28, 31), "day"),

示例:

LocalDate parse = LocalDate.parse("02.2017", f);
System.out.println(parse.getDayOfMonth());

输出:

28