java.util.SimpleTimezone 什么是 startMode 和 endMode？

Question

我正在尝试 Java 的 SimpleTimeZone，我想了解当我创建新的 SimpleTimeZone 对象时它生成的值。首先，这是我的代码和输出

import java.util.*;

public class SimpleTimeZoneDemo {
    public static void main( String args[] ){
    // create simple time zone object
    SimpleTimeZone stobj = new SimpleTimeZone(820,"GMT");

    // checking initial value     
    System.out.println("Initial value: " + stobj);

    // setting start rule   
    stobj.setStartRule( Calendar.MAY, 2, 3600000);   

    // checking the new value      
    System.out.println("Final value : " + stobj);
} 

它生成的输出是

Initial value: java.util.SimpleTimeZone[id=GMT,offset=820,dstSavings=3600000,
useDaylight=false,startYear=0,startMode=0,startMonth=0,startDay=0,
startDayOfWeek=0,startTime=0,startTimeMode=0,endMode=0,endMonth=0,endDay=0,
endDayOfWeek=0,endTime=0,endTimeMode=0]

Final value : java.util.SimpleTimeZone[id=GMT,offset=820,dstSavings=3600000,
useDaylight=false,startYear=0,startMode=1,startMonth=4,startDay=2,
startDayOfWeek=0,startTime=3600000,startTimeMode=0,endMode=0,
endMonth=0,endDay=0,endDayOfWeek=0,endTime=0,endTimeMode=0]

什么是startMode和endMode？为什么startMode从0变成1？我正在尝试弄清楚它似乎与夏令时有关？

Answer 1

startMode 和 endMode 是内部字段。您无法在公共(public) API 中访问它们。

但是，如果查看源代码，它们会被记录下来:

对于startMode:

Variables specifying the mode of the start rule. Takes the following values:

• DOM_MODE: Exact day of week; e.g., March 1.
• DOW_IN_MONTH_MODE: Day of week in month; e.g., last Sunday in March.
• DOW_GE_DOM_MODE: Day of week after day of month; e.g., Sunday on or after March 15.
• DOW_LE_DOM_MODE: Day of week before day of month; e.g., Sunday on or before March 15.

The setting of this field affects the interpretation of the startDay field.

If useDaylight is false, this value is ignored.

对于endMode:

Variables specifying the mode of the end rule. Takes the following values:

• DOM_MODE: Exact day of week; e.g., March 1.
• DOW_IN_MONTH_MODE: Day of week in month; e.g., last Sunday in March.
• DOW_GE_DOM_MODE: Day of week after day of month; e.g., Sunday on or after March 15.
• DOW_LE_DOM_MODE: Day of week before day of month; e.g., Sunday on or before March 15.

The setting of this field affects the interpretation of the endDay field.

If useDaylight is false, this value is ignored.

在您的代码中，第一种情况下 startMode 为 0，因为它未初始化，因此 int 采用其默认值。它更改为 1，因为您将开始规则设置为特定日期，因此模式变为 DOM_MODE = 1。请注意，endMode 保持为 0，因为未设置结束规则。