时间戳

首页 > 解决方案 > 有人请解释 Calendar.get(cal.DAY_OF_WEEK) 如何在 cal.DAY_OF_WEEK 是默认值且未修改时给出正确的输出？

java - 有人请解释 Calendar.get(cal.DAY_OF_WEEK) 如何在 cal.DAY_OF_WEEK 是默认值且未修改时给出正确的输出？

问题描述

我想得到日期的日期。当我在 cal.set(year,month-1,day) 中设置日期时，设置日历字段YEAR、MONTH、DAY_OF_MONTH、HOUR_OF_DAY 和 MINUTE的值。保留其他字段的先前值。因此，当我执行 cal.DAY_OF_WEEK 时，我将获得已经存在的值。但是 cal.get(cal.DAY_OF_WEEK) 如何给出正确的值？（如 java 文档中所述，public int get(int field)返回给定日历字段的值。）我不明白如何在此函数中传递整数值（作为未修改的日历字段）给出正确的输出。

public static String findDay() {
 Calendar cal = Calendar.getInstance();
 cal.set(2019,1,15);
 System.out.println(cal.toString());
 System.out.println(cal.DAY_OF_WEEK); //7 which is unchanged by cal.set
 System.out.println(cal.get(cal.DAY_OF_WEEK)); //6
 return "";

}

代码输出：

java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Etc/UTC",offset=0,dstSavings=0,useDaylight=false,transi
tions=0,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2019,MONTH=1,WEEK_OF_YEAR=7,WEEK_OF_MONTH=3,DAY_OF_MONTH=15,DAY_OF_YEAR=46,DAY_OF_WEEK=6,DAY_OF_WEEK_IN
_MONTH=3,AM_PM=0,HOUR=11,HOUR_OF_DAY=11,MINUTE=38,SECOND=14,MILLISECOND=374,ZONE_OFFSET=0,DST_OFFSET=0]    
7
6

标签： javacalendardayofweek

解决方案

如果您查看Calendarclass 的 java doc，它清楚地提到了cal.DAY_OF_WEEK. 它只表示字段的编号，该get()方法接受字段编号并返回其值。您可以将 的值视为该方法从中检索值cal.DAY_OF_WEEK的数组的索引。get()请参阅下面的get()方法文档。

Returns the value of the given calendar field. In lenient mode,
 * all calendar fields are normalized. In non-lenient mode, all
 * calendar fields are validated and this method throws an
 * exception if any calendar fields have out-of-range values. The
 * normalization and validation are handled by the
 * {@link #complete()} method, which process is calendar

推荐阅读