Java8中为年月新增了类YearMonth，可以用来表示卡片过期时间等问题。

1.YearMonth

默认格式为：2007-12

1.1 部分源码

* * @implSpec * This class is immutable and thread-safe. * * @since 1.8 */ public final class YearMonth implements Temporal, TemporalAdjuster, Comparable, Serializable { /** * Serialization version. */ private static final long serialVersionUID = 4183400860270640070L; /** * Parser. */ private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder() .appendValue(YEAR, 4, 10, SignStyle.EXCEEDS_PAD) .appendLiteral('-') .appendValue(MONTH_OF_YEAR, 2) .toFormatter(); /** * The year. */ private final int year; /** * The month-of-year, not null. */ private final int month;

通过源码可以看出使用final修饰YearMonth，YearMonth是线程安全类，同时实现了Temporal, TemporalAdjuster, Comparable, Serializable接口，有属性读取，设置和加减等功能。

Java日期时间API系列26

1.2 创建和基本使用

YearMonth yearMonth = YearMonth.now(); YearMonth yearMonth2 = YearMonth.of(2020, 4);

    System.out.println(yearMonth);
    System.out.println(yearMonth2);
    YearMonth yearMonth3 \= YearMonth.parse("2020-05");
    System.out.println(yearMonth3);
    
    YearMonth yearMonth4 \= yearMonth3.plusMonths(1);
    System.out.println(yearMonth4);

输出：

2020-03 2020-04 2020-05 2020-06

2.应用

2.1 转换

如Date转YearMonth，YearMonth转Date等

/** * Date转YearMonth * @param date * @return */ public static YearMonth toYearMonth(Date date){ LocalDate localDate = toLocalDate(date); return YearMonth.of(localDate.getYear(), localDate.getMonthValue()); } /** * LocalDateTime转YearMonth * @param localDateTime * @return */ public static YearMonth toYearMonth(LocalDateTime localDateTime){ LocalDate localDate = toLocalDate(localDateTime); return YearMonth.of(localDate.getYear(), localDate.getMonthValue()); } /** * LocalDate转YearMonth * @param localDate * @return */ public static YearMonth toYearMonth(LocalDate localDate){ Objects.requireNonNull(localDate, "localDate"); return YearMonth.of(localDate.getYear(), localDate.getMonthValue()); } /** * Instant转YearMonth * @param instant * @return */ public static YearMonth toYearMonth(Instant instant){ LocalDate localDate = toLocalDate(instant); return YearMonth.of(localDate.getYear(), localDate.getMonthValue()); } /** * ZonedDateTime转YearMonth * @param zonedDateTime * @return */ public static YearMonth toYearMonth(ZonedDateTime zonedDateTime){ LocalDate localDate = toLocalDate(zonedDateTime); return YearMonth.of(localDate.getYear(), localDate.getMonthValue()); } /** * YearMonth转Date * 注意dayOfMonth范围：1到31之间，最大值根据月份确定特殊情况，如2月闰年29，非闰年28 * 如果要转换为当月最后一天，可以使用下面方法：toDateEndOfMonth(YearMonth) * @param yearMonth * @param dayOfMonth * @return */ public static Date toDate(YearMonth yearMonth, int dayOfMonth) { Objects.requireNonNull(yearMonth, "yearMonth"); return toDate(yearMonth.atDay(dayOfMonth)); } /** * YearMonth转Date，转换为当月第一天 * @param yearMonth * @return */ public static Date toDateStartOfMonth(YearMonth yearMonth) { return toDate(yearMonth, 1); } /** * YearMonth转Date，转换为当月最后一天 * @param yearMonth * @return */ public static Date toDateEndOfMonth(YearMonth yearMonth) { Objects.requireNonNull(yearMonth, "yearMonth"); return toDate(yearMonth.atEndOfMonth()); } /** * YearMonth转LocalDate * 注意dayOfMonth范围：1到31之间，最大值根据月份确定特殊情况，如2月闰年29，非闰年28 * 如果要转换为当月最后一天，可以使用下面方法：toLocalDateEndOfMonth(YearMonth) * @param yearMonth * @param dayOfMonth * @return */ public static LocalDate toLocalDate(YearMonth yearMonth, int dayOfMonth) { Objects.requireNonNull(yearMonth, "yearMonth"); return yearMonth.atDay(dayOfMonth); } /** * YearMonth转LocalDate，转换为当月第一天 * @param yearMonth * @return */ public static LocalDate toLocalDateStartOfMonth(YearMonth yearMonth) { return toLocalDate(yearMonth, 1); } /** * YearMonth转LocalDate，转换为当月最后一天 * @param yearMonth * @return */ public static LocalDate toLocalDateEndOfMonth(YearMonth yearMonth) { Objects.requireNonNull(yearMonth, "yearMonth"); return yearMonth.atEndOfMonth(); }

测试代码：

@Test public void yearMonthConverterTest(){ System.out.println("===================yearMonthConverterTest====================="); Date date = new Date(); System.out.println(date); YearMonth yearMonth = DateTimeConverterUtil.toYearMonth(date); System.out.println(yearMonth);

    Date date1 \= DateTimeConverterUtil.toDate(yearMonth, 15); //转换为当月第一天
    Date date2 = DateTimeConverterUtil.toDateStartOfMonth(yearMonth); //转换为当月最后一天
    Date date3 = DateTimeConverterUtil.toDateEndOfMonth(yearMonth);
    System.out.println(date1);
    System.out.println(date2);
    System.out.println(date3);
    
    LocalDate LocalDate1 \= DateTimeConverterUtil.toLocalDate(yearMonth, 15); //转换为当月第一天
    LocalDate LocalDate2 = DateTimeConverterUtil.toLocalDateStartOfMonth(yearMonth); //转换为当月最后一天
    LocalDate LocalDate3 = DateTimeConverterUtil.toLocalDateEndOfMonth(yearMonth);
    System.out.println(LocalDate1);
    System.out.println(LocalDate2);
    System.out.println(LocalDate3);
}

输出:

===================yearMonthConverterTest===================== Fri Mar 20 23:41:41 CST 2020 2020-03 Sun Mar 15 00:00:00 CST 2020 Sun Mar 01 00:00:00 CST 2020 Tue Mar 31 00:00:00 CST 2020 2020-03-15 2020-03-01 2020-03-31

2.2 计算

获取起始日期中间的日期列表，获取指定月份的日期列表，判断是否过期等等

/** * 获取指定区间的时间列表，包含起始 * @param startInclusive * @param endInclusive * @return */ public static List getLocalDateTimeList(LocalDateTime startInclusive, LocalDateTime endInclusive){ Objects.requireNonNull(startInclusive, "startInclusive"); Objects.requireNonNull(endInclusive, "endInclusive"); if(startInclusive.isAfter(endInclusive)){ throw new DateTimeException("startInclusive must before or equal endInclusive!"); } List localDateTimeList = new ArrayList(); long days = betweenTotalDays(startInclusive, endInclusive)+1; for(long i=0; i<days; i++){ localDateTimeList.add(startInclusive.plusDays(i)); } return localDateTimeList; } /** * 获取指定区间的时间列表，包含起始 * @param startInclusive * @param endInclusive * @return */ public static List getLocalDateList(LocalDate startInclusive, LocalDate endInclusive){ return getLocalDateTimeList(DateTimeConverterUtil.toLocalDateTime(startInclusive), DateTimeConverterUtil.toLocalDateTime(endInclusive)).stream() .map(localDateTime -> localDateTime.toLocalDate()).collect(Collectors.toList()); } /** * 获取指定区间的时间列表，包含起始 * @param startInclusive * @param endInclusive * @return */ public static List getDateList(Date startInclusive, Date endInclusive){ return getLocalDateTimeList(DateTimeConverterUtil.toLocalDateTime(startInclusive), DateTimeConverterUtil.toLocalDateTime(endInclusive)).stream() .map(localDateTime -> DateTimeConverterUtil.toDate(localDateTime)).collect(Collectors.toList()); } /** * 获取指定年月的所有日期列表 * @param YearMonth * @return */ public static List getLocalDateList(YearMonth yearMonth){ Objects.requireNonNull(yearMonth, "yearMonth"); List localDateList = new ArrayList(); long days = yearMonth.lengthOfMonth(); LocalDate localDate = DateTimeConverterUtil.toLocalDateStartOfMonth(yearMonth); for(long i=0; i<days; i++){ localDateList.add(plusDays(localDate, i)); } return localDateList; } /** * 获取指定年月的所有日期列表 * @param yearMonthStr yyyy-MM * @return */ public static List getLocalDateList(String yearMonthStr){ Objects.requireNonNull(yearMonthStr, "yearMonthStr"); YearMonth yearMonth = YearMonth.parse(yearMonthStr); return getLocalDateList(yearMonth); } /** * 获取指定年月的所有日期列表 * @param yearMonth * @return */ public static List getLocalDateTimeList(YearMonth yearMonth){ return getLocalDateList(yearMonth).stream() .map(localDate -> DateTimeConverterUtil.toLocalDateTime(localDate)).collect(Collectors.toList()); } /** * 获取指定年月的所有日期列表 * @param yearMonthStr yyyy-MM * @return */ public static List getLocalDateTimeList(String yearMonthStr){ return getLocalDateList(yearMonthStr).stream() .map(localDate -> DateTimeConverterUtil.toLocalDateTime(localDate)).collect(Collectors.toList()); } /** * 获取指定年月的所有日期列表 * @param yearMonthStr yyyy-MM * @return */ public static List getDateList(String yearMonthStr){ return getLocalDateList(yearMonthStr).stream().map(localDate -> DateTimeConverterUtil.toDate(localDate)) .collect(Collectors.toList()); } /** * 判断是否过期，（输入年月小于当前年月） * @param yearMonth * @return */ public static boolean isExpiry(YearMonth yearMonth){ Objects.requireNonNull(yearMonth, "yearMonth"); if(yearMonth.isBefore(YearMonth.now())){ return true; } return false; } /** * 判断是否过期，（输入年月小于当前年月） * @param yearMonthStr yyyy-MM * @return */ public static boolean isExpiry(String yearMonthStr){ Objects.requireNonNull(yearMonthStr, "yearMonthStr"); YearMonth yearMonth = YearMonth.parse(yearMonthStr); return isExpiry(yearMonth); }

测试代码：

/** * yearMonth测试 */ @Test public void yearMonthTest(){ //是否过期 System.out.println(DateTimeCalculatorUtil.isExpiry("2020-03")); //获取指定年月的所有日期列表 List dateList = DateTimeCalculatorUtil.getDateList("2020-03"); dateList.stream().forEach(date->{ System.out.println(DateTimeFormatterUtil.formatToDateStr(date)); });

    System.out.println("========================"); //获取指定区间的时间列表，包含起始
    List<Date> dateList2 = DateTimeCalculatorUtil.getDateList(dateList.get(0), dateList.get(dateList.size()-1));
    dateList2.stream().forEach(date\->{
        System.out.println(DateTimeFormatterUtil.formatToDateStr(date));
    });
    
}

输出：

false 2020-03-01 2020-03-02 2020-03-03 2020-03-04 2020-03-05 2020-03-06 2020-03-07 2020-03-08 2020-03-09 2020-03-10 2020-03-11 2020-03-12 2020-03-13 2020-03-14 2020-03-15 2020-03-16 2020-03-17 2020-03-18 2020-03-19 2020-03-20 2020-03-21 2020-03-22 2020-03-23 2020-03-24 2020-03-25 2020-03-26 2020-03-27 2020-03-28 2020-03-29 2020-03-30 2020-03-31 ======================== 2020-03-01 2020-03-02 2020-03-03 2020-03-04 2020-03-05 2020-03-06 2020-03-07 2020-03-08 2020-03-09 2020-03-10 2020-03-11 2020-03-12 2020-03-13 2020-03-14 2020-03-15 2020-03-16 2020-03-17 2020-03-18 2020-03-19 2020-03-20 2020-03-21 2020-03-22 2020-03-23 2020-03-24 2020-03-25 2020-03-26 2020-03-27 2020-03-28 2020-03-29 2020-03-30 2020-03-31

源代码地址：https://github.com/xkzhangsan/xk-time