如何根据当前日期（包括 java 中的当前日期）获取最近三个月的第一个日期和最后一个日期？

Question

我想根据月份对值进行分类，以便根据当前月份（包括当前月份值）过滤过去三个月的第一个和最后一个日期所需的那些值。这里有多少个月是参数。我想要所有月份的第一个日期和最后一个日期的列表。任何相同的逻辑都会有所帮助。

例如：-

     //     parameters 
          int lastMonths = 3;
          date currentDate= 26-04-2019;

 //expected output
 current month is 04-2019 ,1st date is 1-04-2019 and last date is 30-04-2019 
 previous month is 03-2019, 1st date is 01-03-2019 and last date is 31-03-2019
 previous month is 02-2019, 1st date is 01-02-2019 and last date is 28-02-2019

Answer 1

如果您需要 Date 对象，那么以下内容就可以了

        Date date = getDate(targetDate);
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.add(Calendar.MONTH, -3);
        calendar.set(Calendar.DAY_OF_MONTH, 1);

        // calendar.getTime()
        // The line above returns Date object

如果你需要一个普通的字符串，那么你可以通过简单地使用 org.joda.time 库中的 DateTimeFormatter 并使用它的 print() 方法来以任何你想要的方式格式化它calendar.getTimeInMillis().

Answer 2

重要的是 - 有大量的库可以满足您的这种特定需求，但我想依靠一个可以完成工作并且实际上是为（您的一些......）这些用例设计的库 - Java.time.LocalDate 库（已内置于 Java 8）

import java.time.LocalDate;

LocalDate now = LocalDate.now(); // 2019-04-26

为了获取一个月的第一天和最后一天，您可以使用：

LocalDate start = YearMonth.now().atDay(1);

（当然现在可以是其他月份）

LocalDate end = YearMonth.now().atEndOfMonth();

你可以专门用在一/两个月，或者配合一些for循环。以下示例：
1。具体调用：

LocalDate earlierOneMonth = now.minusMonths(1); // 2019-03-26
earlierOneMonth.getDay(); // 26

2。 For循环：（所以你需要像数组/列表这样的东西来存储这些值......）

for(int i=0; i < lastMonths - 1; i++){
   arr(i) = now.minusMonths(i + 1);

}

此外，为了获取月份名称，您可以使用 ->

earlierOneMonth.getMonth(); // APRIL
earlierOneMonth.getMonth.getValue(); // 04

最后，为了得到年份，你可以使用 ->

earlier.getYear(); // 2019

一旦您获得了所有所需的值，您就可以按照您的要求将它们打印出来，并获得预期的输出：

 "current month is" + nowMonth + "-" + nowYear + " ,1st date is" +  nowDay + "-" + nowMonth + "-" + nowYear + " and last date is ...

让我知道是否足够清楚:)

Answer 3

Use java.util.Calendar for addition and subraction in date

和

java.text.DateFormat to format date

    DateFormat format = new SimpleDateFormat("dd-MM-yyyy", Locale.US);
    DateFormat monthFormat = new SimpleDateFormat("MM-yyyy", Locale.US);
    Calendar cal = Calendar.getInstance();
    cal.setTime(format.parse("26-04-2019"));
    for (int i = 0; i < 3; i++){
        System.out.println("currentDate: " + monthFormat.format(cal.getTime())); // print current month

        cal.set(Calendar.DAY_OF_MONTH, 1);
        System.out.println("first date: " + format.format(cal.getTime())); // print first date

        cal.add(Calendar.MONTH, 1);
        cal.set(Calendar.DAY_OF_MONTH, 1);
        cal.add(Calendar.DATE, -1);

        System.out.println("last date: " + format.format(cal.getTime())); // print last date


        cal.add(Calendar.MONTH, -1);
    }

Answer 4

    int lastMonths = 3;

    Calendar calendar = Calendar.getInstance();

    int year = calendar.get(Calendar.YEAR);
    int month = calendar.get(Calendar.MONTH) + 1;
    int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);

    DateFormat monthYearFormat = new SimpleDateFormat("MM-yyyy");

    for (int i = 0; i < lastMonths; i++) {

        int monthOfYear = month - i;

        // if month is january, reset couter and month
        if(monthOfYear == 0) {
            month = 13;
            year -= 1;
            i = 0;
            continue;
        }

        // get last day of month (month length)
        YearMonth yearMonth = YearMonth.of(year, monthOfYear);
        int firstDay = 1;
        int lastDay  = yearMonth.lengthOfMonth();

        // create date with given year, month and day
        Date date = new GregorianCalendar(year, monthOfYear - 1, firstDay).getTime();

        String monthAndYear = monthYearFormat.format(date);

        String currentOrPrevious;

        if (i == 0) {
            currentOrPrevious = "current";
        } else {
            currentOrPrevious = "previous";
        }

        String output = String.format("%s month is %s, 1st date is %02d-%s and last date is %d-%s", currentOrPrevious, monthAndYear, firstDay, monthAndYear, lastDay, monthAndYear);

        System.out.println(output);
    }

输出：

current month is 04-2019, 1st date is 01-04-2019 and last date is 30-04-2019
previous month is 03-2019, 1st date is 01-03-2019 and last date is 31-03-2019
previous month is 02-2019, 1st date is 01-02-2019 and last date is 28-02-2019

Answer 5

    LocalDate currentDate = LocalDate.of(2019, 4, 26);//current date
    System.out.println(currentDate);
    int lastMonths = 3;//number of months
    LocalDate prevDate = null;
    LocalDate start = null;
    LocalDate end = null;

    for(int i = 0; i < lastMonths; i++) {
        if(prevDate == null) {
            start = currentDate.withDayOfMonth(1);//First day of current month
            end = currentDate.withDayOfMonth(currentDate.lengthOfMonth());//Last day of current month
            prevDate = currentDate.minusMonths(1);//subtracting one month from current month 
        } else {
            start = prevDate.withDayOfMonth(1);//First day of previous month
            end = prevDate.withDayOfMonth(prevDate.lengthOfMonth());//Last day of previous month
            prevDate = prevDate.minusMonths(1);//subtracting one month from previous month
        }
        System.out.println(start + " " + end);
    }

输出：

2019-04-26
2019-04-01 2019-04-30
2019-03-01 2019-03-31
2019-02-01 2019-02-28

参考： Get first and last day of month using threeten, LocalDate

Answer 6

tl;博士

YearMonth.now().minusMonths( 3 ).atDay( 1 )      // Get the first day of the month of three months ago. Returns `LocalDate` object.
YearMonth.now().minusMonths( 3 ).atEndOfMonth()  // Get the last day of the month of three months ago. Returns `LocalDate` object.

`YearMonth`

你真的很在乎月份。日期是次要的。所以关注月份。 Java 有一个 class ！

YearMonth class 表示特定年份的特定月份。

ZoneId z = ZoneId.of( "America/Edmonton" ) ;
YearMonth currentYm = YearMonth.now( z ) ;

收集您的月息。

List< YearMonth > yms = new ArrayList<>() ;
int limit = 3 ; // We want current month plus three previous months. 
for( int i = 0 ; i <= limit ; i ++ ) {
    YearMonth ym = currentYm.minusMonths( i ) ;
    yms.add( ym ) ;
}

当你需要日期时，循环列表。让 YearMonth 确定该月的第一天和最后一天。

for( YearMonth ym : yms ) {
    System.out.println( "YearMonth: " + ym + " starts: " + ym.atDay( 1 ) +  " ends: " + ym.atEndOfMonth() ) ; 
}

看到这个code run live at IdeOne.com。

YearMonth: 2019-04 starts: 2019-04-01 ends: 2019-04-30

YearMonth: 2019-03 starts: 2019-03-01 ends: 2019-03-31

YearMonth: 2019-02 starts: 2019-02-01 ends: 2019-02-28

YearMonth: 2019-01 starts: 2019-01-01 ends: 2019-01-31

如何根据当前日期（包括 java 中的当前日期）获取最近三个月的第一个日期和最后一个日期？

How to get last three months first date and last date based on current date including current date in java?

java

calendar

date

localdate

tl;博士

`YearMonth`