时间格式对照表

	Symbol  Meaning                     Presentation      Examples
   ------  -------                     ------------      -------
    G       era                         text              AD; Anno Domini; A
    u       year                        year              2004; 04
    y       year-of-era                 year              2004; 04
    D       day-of-year                 number            189
    M/L     month-of-year               number/text       7; 07; Jul; July; J
    d       day-of-month                number            10
 
    Q/q     quarter-of-year             number/text       3; 03; Q3; 3rd quarter
    Y       week-based-year             year              1996; 96
    w       week-of-week-based-year     number            27
    W       week-of-month               number            4
    E       day-of-week                 text              Tue; Tuesday; T
    e/c     localized day-of-week       number/text       2; 02; Tue; Tuesday; T
    F       week-of-month               number            3
 
    a       am-pm-of-day                text              PM
    h       clock-hour-of-am-pm (1-12)  number            12
    K       hour-of-am-pm (0-11)        number            0
    k       clock-hour-of-am-pm (1-24)  number            0
 
    H       hour-of-day (0-23)          number            0
    m       minute-of-hour              number            30
    s       second-of-minute            number            55
    S       fraction-of-second          fraction          978
    A       milli-of-day                number            1234
    n       nano-of-second              number            987654321
    N       nano-of-day                 number            1234000000
 
    V       time-zone ID                zone-id           America/Los_Angeles; Z; -08:30
    z       time-zone name              zone-name         Pacific Standard Time; PST
    O       localized zone-offset       offset-O          GMT+8; GMT+08:00; UTC-08:00;
    X       zone-offset 'Z' for zero    offset-X          Z; -08; -0830; -08:30; -083015; -08:30:15;
    x       zone-offset                 offset-x          +0000; -08; -0830; -08:30; -083015; -08:30:15;
    Z       zone-offset                 offset-Z          +0000; -0800; -08:00;
 
    p       pad next                    pad modifier      1
 
    '       escape for text             delimiter
    ''      single quote                literal           '
    [       optional section start
    ]       optional section end
    #       reserved for future use
    {       reserved for future use
    }       reserved for future use

DateTimeFormatter相关

常规使用

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");

复杂格式实现

// 时间格式非常规
new DateTimeFormatterBuilder()
            .appendValue(YEAR, 4)
            .appendLiteral('0')// 针对带数字的只能用这种方式
            .appendValue(MONTH_OF_YEAR, 2)
            .toFormatter()
            

// 202212 -> 20221201
new DateTimeFormatterBuilder()
            .appendValue(YEAR, 4)
            .appendValue(MONTH_OF_YEAR, 2)
            .parseDefaulting(ChronoField.DAY_OF_MONTH, 1)// 需要带默认值的
            .toFormatter();