如何获得一年的开始和结束日期？

Question

我必须使用Java Date类来解决这个问题(它与我无法控制的东西接口).

如何获取一年的开始和结束日期,然后遍历每个日期？

Answer 1

java.time

使用java.timeJava 8及更高版本中内置的库.特别是LocalDate和TemporalAdjusters班级.

import java.time.LocalDate
import static java.time.temporal.TemporalAdjusters.firstDayOfYear
import static java.time.temporal.TemporalAdjusters.lastDayOfYear

LocalDate now = LocalDate.now(); // 2015-11-23
LocalDate firstDay = now.with(firstDayOfYear()); // 2015-01-01
LocalDate lastDay = now.with(lastDayOfYear()); // 2015-12-31

如果您需要添加时间信息,可以使用任何可用LocalDate的LocalDateTime转换方式

lastDay.atStartOfDay(); // 2015-12-31T00:00

Answer 2

Calendar cal = Calendar.getInstance();
cal.set(Calendar.YEAR, 2014);
cal.set(Calendar.DAY_OF_YEAR, 1);    
Date start = cal.getTime();

//set date to last day of 2014
cal.set(Calendar.YEAR, 2014);
cal.set(Calendar.MONTH, 11); // 11 = december
cal.set(Calendar.DAY_OF_MONTH, 31); // new years eve

Date end = cal.getTime();

//Iterate through the two dates 
GregorianCalendar gcal = new GregorianCalendar();
gcal.setTime(start);
while (gcal.getTime().before(end)) {
    gcal.add(Calendar.DAY_OF_YEAR, 1);
    //Do Something ...
}

Answer 3

    // suppose that I have the following variable as input
    int year=2011;
    Calendar calendarStart=Calendar.getInstance();
    calendarStart.set(Calendar.YEAR,year);
    calendarStart.set(Calendar.MONTH,0);
    calendarStart.set(Calendar.DAY_OF_MONTH,1);
    // returning the first date
    Date startDate=calendarStart.getTime();

    Calendar calendarEnd=Calendar.getInstance();
    calendarEnd.set(Calendar.YEAR,year);
    calendarEnd.set(Calendar.MONTH,11);
    calendarEnd.set(Calendar.DAY_OF_MONTH,31);

    // returning the last date
    Date endDate=calendarEnd.getTime();

要迭代，您应该使用日历对象并增加 day_of_month 变量

希望它可以帮助

Answer 4

 Calendar cal = new GregorianCalendar();
     cal.set(Calendar.DAY_OF_YEAR, 1);
     System.out.println(cal.getTime().toString());
     cal.set(Calendar.DAY_OF_YEAR, 366); // for leap years
     System.out.println(cal.getTime().toString());

Answer 5

如果您正在寻找单行表达式，我通常使用这个：

new SimpleDateFormat("yyyy-MM-dd").parse(String.valueOf(new java.util.Date().getYear())+"-01-01")

Answer 6

比斯里尼的答案有所改进。
使用 确定一年中的最后一个日期Calendar.getActualMaximum。

Calendar cal = Calendar.getInstance();

calDate.set(Calendar.DAY_OF_YEAR, 1);
Date yearStartDate = calDate.getTime();

calDate.set(Calendar.DAY_OF_YEAR, calDate.getActualMaximum(Calendar.DAY_OF_YEAR));
Date yearEndDate = calDate.getTime();