特定年份特定月份的天数？

如何知道特定年份的特定月份有多少天？

String date = "2010-01-19";
String[] ymd = date.split("-");
int year = Integer.parseInt(ymd[0]);
int month = Integer.parseInt(ymd[1]);
int day = Integer.parseInt(ymd[2]);
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR,year);
calendar.set(Calendar.MONTH,month);
int daysQty = calendar.getDaysNumber(); // Something like this
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最佳答案

Java 8及更高版本

@ Warren M. Nocos. 如果您试图使用 Java8的新 日期和时间 API，可以使用 java.time.YearMonth类。

// Get the number of days in that month
YearMonth yearMonthObject = YearMonth.of(1999, 2);
int daysInMonth = yearMonthObject.lengthOfMonth(); //28

测试: 在闰年尝试一个月:

yearMonthObject = YearMonth.of(2000, 2);
daysInMonth = yearMonthObject.lengthOfMonth(); //29

Java7及更早版本

创建一个日历，设置年和月并使用 getActualMaximum

int iYear = 1999;
int iMonth = Calendar.FEBRUARY; // 1 (months begin with 0)
int iDay = 1;


// Create a calendar object and set year and month
Calendar mycal = new GregorianCalendar(iYear, iMonth, iDay);


// Get the number of days in that month
int daysInMonth = mycal.getActualMaximum(Calendar.DAY_OF_MONTH); // 28

Test : 尝试闰年的一个月:

mycal = new GregorianCalendar(2000, Calendar.FEBRUARY, 1);
daysInMonth= mycal.getActualMaximum(Calendar.DAY_OF_MONTH);      // 29
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日历代码

如果你必须使用 java.util.Calendar，我怀疑你想:

int days = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);

Joda 时间代码

然而，就我个人而言，我建议首先使用 乔达时间而不是 java.util.{Calendar, Date}，在这种情况下，您可以使用:

int days = chronology.dayOfMonth().getMaximumValue(date);

请注意，与其分别解析字符串值，不如获取用于解析字符串值的日期/时间 API。在 Joda Time，你可以使用 DateTimeFormatter。

小开

你可以使用 Calendar.getActualMaximum方法:

Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, month);
int numDays = calendar.getActualMaximum(Calendar.DATE);
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if (month == 4 || month == 6 || month == 9 || month == 11) {
daysInMonth = 30;
} else if (month == 2) {
daysInMonth = (leapYear) ? 29 : 28;
else {
daysInMonth = 31;
}
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import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;


/*
* 44. Return the number of days in a month
* , where month and year are given as input.
*/
public class ex44 {
public static void dateReturn(int m,int y)
{
int m1=m;
int y1=y;
String str=" "+ m1+"-"+y1;
System.out.println(str);
SimpleDateFormat sd=new SimpleDateFormat("MM-yyyy");


try {
Date d=sd.parse(str);
System.out.println(d);
Calendar c=Calendar.getInstance();
c.setTime(d);
System.out.println(c.getActualMaximum(Calendar.DAY_OF_MONTH));
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}


}
public static void main(String[] args) {
dateReturn(2,2012);




}


}
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String date = "11-02-2000";
String[] input = date.split("-");
int day = Integer.valueOf(input[0]);
int month = Integer.valueOf(input[1]);
int year = Integer.valueOf(input[2]);
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR,year);
cal.set(Calendar.MONTH,month-1);
cal.set(Calendar.DATE, day);
//since month number starts from 0 (i.e jan 0, feb 1),
//we are subtracting original month by 1
int days = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
System.out.println(days);
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java.time.LocalDate

从 Java 1.8开始，您可以在 java.time.LocalDate上使用方法 lengthOfMonth:

LocalDate date = LocalDate.of(2010, 1, 19);
int days = date.lengthOfMonth();
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以下方法将提供您在某一特定月份的天数

public static int getNoOfDaysInAMonth(String date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
return (cal.getActualMaximum(Calendar.DATE));
}
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可以使用 Calendar.get斩获最大值方法:

Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, month-1);
int numDays = calendar.getActualMaximum(Calendar.DATE);

而 month-1是’Cause of month 取其原始的 month 数，而 in method 在 Calendar.class 中取下面的参数

public int getActualMaximum(int field) {
throw new RuntimeException("Stub!");
}

(int 字段)如下所示。

public static final int JANUARY = 0;
public static final int NOVEMBER = 10;
public static final int DECEMBER = 11;
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这招对我很管用。

这是一个示例输出

import java.util.*;


public class DaysInMonth {


public static void main(String args []) {


Scanner input = new Scanner(System.in);
System.out.print("Enter a year:");


int year = input.nextInt(); //Moved here to get input after the question is asked


System.out.print("Enter a month:");
int month = input.nextInt(); //Moved here to get input after the question is asked


int days = 0; //changed so that it just initializes the variable to zero
boolean isLeapYear = (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);


switch (month) {
case 1:
days = 31;
break;
case 2:
if (isLeapYear)
days = 29;
else
days = 28;
break;
case 3:
days = 31;
break;
case 4:
days = 30;
break;
case 5:
days = 31;
break;
case 6:
days = 30;
break;
case 7:
days = 31;
break;
case 8:
days = 31;
break;
case 9:
days = 30;
break;
case 10:
days = 31;
break;
case 11:
days = 30;
break;
case 12:
days = 31;
break;
default:
String response = "Have a Look at what you've done and try again";
System.out.println(response);
System.exit(0);
}


String response = "There are " + days + " Days in Month " + month + " of Year " + year + ".\n";
System.out.println(response); // new line to show the result to the screen.
}
} //abhinavsthakur00@gmail.com
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在 Java8中，您可以使用从日期字段获取 ValueRange。

LocalDateTime dateTime = LocalDateTime.now();


ChronoField chronoField = ChronoField.MONTH_OF_YEAR;
long max = dateTime.range(chronoField).getMaximum();

这允许您对字段进行参数化。

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这就是数学方法:

年份(例如2012年)、月份(1至12) :

int daysInMonth = month !== 2 ?
31 - (((month - 1) % 7) % 2) :
28 + (year % 4 == 0 ? 1 : 0) - (year % 100 == 0 ? 1 : 0) + (year % 400 == 0 ? 1 : 0)
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public class Main {


private static LocalDate local=LocalDate.now();
public static void main(String[] args) {


int month=local.lengthOfMonth();
System.out.println(month);


}
}
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应该避免使用过时的 Calendar API。

在 Java8或更高版本中，这可以通过 YearMonth完成。

示例代码:

int year = 2011;
int month = 2;
YearMonth yearMonth = YearMonth.of(year, month);
int lengthOfMonth = yearMonth.lengthOfMonth();
System.out.println(lengthOfMonth);
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就这么简单，不需要进口任何东西

public static int getMonthDays(int month, int year) {
int daysInMonth ;
if (month == 4 || month == 6 || month == 9 || month == 11) {
daysInMonth = 30;
}
else {
if (month == 2) {
daysInMonth = (year % 4 == 0) ? 29 : 28;
} else {
daysInMonth = 31;
}
}
return daysInMonth;
}
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String  MonthOfName = "";
int number_Of_DaysInMonth = 0;


//year,month
numberOfMonth(2018,11); // calling this method to assign values to the variables MonthOfName and number_Of_DaysInMonth


System.out.print("Number Of Days: "+number_Of_DaysInMonth+"   name of the month: "+  MonthOfName );


public void numberOfMonth(int year, int month) {
switch (month) {
case 1:
MonthOfName = "January";
number_Of_DaysInMonth = 31;
break;
case 2:
MonthOfName = "February";
if ((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))) {
number_Of_DaysInMonth = 29;
} else {
number_Of_DaysInMonth = 28;
}
break;
case 3:
MonthOfName = "March";
number_Of_DaysInMonth = 31;
break;
case 4:
MonthOfName = "April";
number_Of_DaysInMonth = 30;
break;
case 5:
MonthOfName = "May";
number_Of_DaysInMonth = 31;
break;
case 6:
MonthOfName = "June";
number_Of_DaysInMonth = 30;
break;
case 7:
MonthOfName = "July";
number_Of_DaysInMonth = 31;
break;
case 8:
MonthOfName = "August";
number_Of_DaysInMonth = 31;
break;
case 9:
MonthOfName = "September";
number_Of_DaysInMonth = 30;
break;
case 10:
MonthOfName = "October";
number_Of_DaysInMonth = 31;
break;
case 11:
MonthOfName = "November";
number_Of_DaysInMonth = 30;
break;
case 12:
MonthOfName = "December";
number_Of_DaysInMonth = 31;
}
}
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如果您不想硬编码年份和月份的值，而想从当前日期和时间中获取值，那么让我们把它变得简单一些:

Date d = new Date();
String myDate = new SimpleDateFormat("dd/MM/yyyy").format(d);
int iDayFromDate = Integer.parseInt(myDate.substring(0, 2));
int iMonthFromDate = Integer.parseInt(myDate.substring(3, 5));
int iYearfromDate = Integer.parseInt(myDate.substring(6, 10));


YearMonth CurrentYear = YearMonth.of(iYearfromDate, iMonthFromDate);
int lengthOfCurrentMonth = CurrentYear.lengthOfMonth();
System.out.println("Total number of days in current month is " + lengthOfCurrentMonth );
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// 1 means Sunday ,2 means Monday .... 7 means Saturday
//month starts with 0 (January)


MonthDisplayHelper monthDisplayHelper = new MonthDisplayHelper(2019,4);
int numbeOfDaysInMonth = monthDisplayHelper.getNumberOfDaysInMonth();
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我会选择这样的解决方案:

int monthNr = getMonth();
final Month monthEnum = Month.of(monthNr);
int daysInMonth;
if (monthNr == 2) {
int year = getYear();
final boolean leapYear = IsoChronology.INSTANCE.isLeapYear(year);
daysInMonth = monthEnum.length(leapYear);
} else {
daysInMonth = monthEnum.maxLength();
}

如果月份不是2月份(92% 的病例) ，那么只取决于月份，不涉及年份效率更高。这样，你就不必通过逻辑来判断今年是否是闰年，而且92% 的情况下你也不需要知道是闰年。 它仍然是干净和非常可读的代码。

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最佳和绩效方差:

public static int daysInMonth(int month, int year) {
if (month != 2) {
return 31 - (month - 1) % 7 % 2;
}
else {
if ((year & 3) == 0 && ((year % 25) != 0 || (year & 15) == 0)) { // leap year
return 29;
} else {
return 28;
}
}
}

有关跳跃算法的详细信息，请查看 给你

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特定年份的天数-Java8 + 解决方案

Year.now().length()
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另一种解决方案是使用 Calendar对象。获取当前日期并设置日期，使其成为每月的第一天。然后加上一个月，再减去一天，得到当前月份的最后一天。最后获取日期以获取该月的天数。

Calendar today = getInstance(TimeZone.getTimeZone("UTC"));


Calendar currMonthLastDay = getInstance(TimeZone.getTimeZone("UTC"));
currMonthLastDay.clear();
currMonthLastDay.set(YEAR, today.get(YEAR));
currMonthLastDay.set(MONTH, today.get(MONTH));
currMonthLastDay.set(DAY_OF_MONTH, 1);
currMonthLastDay.add(MONTH, 1);
currMonthLastDay.add(DAY_OF_MONTH, -1);


Integer daysInMonth = currMonthLastDay.get(DAY_OF_MONTH);

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