Java 日期解析问题 - SimpleDateFormat 自动递减月份

Question

我尝试使用以下模式从字符串中解析日期：

final static String DATE_RU_PATTERN = "dd.MM.yyyy"; 
private static SimpleDateFormat ruFormatter = new SimpleDateFormat(DATE_RU_PATTERN);
public static Date GetDateFromStringRuFormat (String dateString){       
    try {       
        return ruFormatter.parse(dateString);
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return null;
}

为什么 ruFormatter.parse(dateString) 给出 Date 和 Month 的递减值？

@Test
public void TestGetDateFromStringRuFormat(){
    final String dateString = "24.09.2015";
    Calendar actualCalendar = Calendar.getInstance();
    Date actualResult = DateFormatHelper.GetDateFromStringRuFormat(dateString);
    actualCalendar.setTime(actualResult);
    assertEquals(9, actualCalendar.get(Calendar.MONTH)); // FAILS 
    assertEquals(24, actualCalendar.get(Calendar.DAY_OF_MONTH));
    assertEquals(2015, actualCalendar.get(Calendar.YEAR));
}

Answer 1

Calendar 喜欢 java.util.Date 从 0 开始计算月份。所以每当你想对月份值做一些有意义的事情时，就给它加 1。

来自Javadoc：

Field number for get and set indicating the month. This is a calendar-specific value. The first month of the year in the Gregorian and Julian calendars is JANUARY which is 0; the last depends on the number of months in a year.

因此您的单元测试应为：

assertEquals(9, actualCalendar.get(Calendar.MONTH) + 1);

Answer 2

日历中的月份 class 从零开始：

JANUARY = 0
FEBRUARY = 1

...

所以 9 月 = 8 (http://docs.oracle.com/javase/1.5.0/docs/api/java/util/Calendar.html#MONTH)。

尝试将测试更改为：

assertEquals(Calendar.SEPTEMBER, actualCalendar.get(Calendar.MONTH));

Java 日期解析问题 - SimpleDateFormat 自动递减月份

Java date parsing issue - SimpleDateFormat automatically decrements month

java

date

simpledateformat