java - 跨 2 个日历年的日历计算存在问题

Question

我正在使用一种根据给定日期字符串计算下周一的方法。

public static String getStartOfNextWeek(String DATE){

String format = "dd.MM.yyyy";SimpleDateFormat df = new SimpleDateFormat(format);

Date date = null;
try {
date = df.parse(DATE);
} catch (ParseException e) {
e.printStackTrace();
}

Calendar cal = Calendar.getInstance();

cal.setTime(date);
int week = cal.get(Calendar.WEEK_OF_YEAR);
int year = cal.get(Calendar.YEAR);

Calendar calendar = new GregorianCalendar();
calendar.clear(); 
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.WEEK_OF_YEAR, week);

//add 8 days to get next weeks Monday

calendar.add(Calendar.DAY_OF_WEEK, 8);

Date startDate = calendar.getTime();

SimpleDateFormat df2 = new SimpleDateFormat("dd.MM.yyyy");

String start = df2.format(startDate);

return start;

这在一个日历年中工作得很好，但是当我传递一个跨越两个日历年的值时，就会出现问题。

例如:

input: 15.12.2014
output: 22.12.2014 CORRECT
input: 22.12.2014
output: 29.12.2014 CORRECT
input: 29.12.2014
output: 6.1.2014 INCORRECT

我意识到错误所在，因为它将 WEEK_OF_YEAR 视为“1”，但将 YEAR 视为“2014”，因此输出在技术上是正确的。完全不符合我的目的。

我如何最好地告诉日历对象我想要第 1 周的下一个星期一，但 2015 年？

Answer 1

更新:Joda-Time项目现已在 maintenance mode ，团队建议迁移到 java.time类。这个答案作为历史完好无损。请参阅my newer Answer .

乔达时间

Joda-Time库，版本 2.5，得到了正确的答案。并且更容易获得。

// Parse input string.
String input = "29.12.2014";
DateTimeFormatter formatter = DateTimeFormat.forPattern( "dd.MM.yyyy" );
LocalDate inputLocalDate = formatter.parseLocalDate( input );

// Find desired Monday.
LocalDate possibleMonday = inputLocalDate.withDayOfWeek( DateTimeConstants.MONDAY ); 

// The possible Monday could be past, present, or future of our input date. Adjust as needed.
LocalDate desiredMonday = null;
if ( possibleMonday.isBefore( inputLocalDate ) || possibleMonday.isEqual( inputLocalDate ) ) {
    desiredMonday = possibleMonday.plusWeeks( 1 ); // If the possible Monday is past or present, add a week to get *next* Monday.
} else {
    desiredMonday = possibleMonday;  // If the possible Monday is future, use it.
}

String output = formatter.print( desiredMonday ); 

转储到控制台。

System.out.println( "input : " + input );
System.out.println( "inputLocalDate : " + inputLocalDate );
System.out.println( "desiredMonday : " + desiredMonday );
System.out.println( "output : " + output );

运行时。

input : 29.12.2014
inputLocalDate : 2014-12-29
desiredMonday : 2015-01-05
output : 05.01.2015