java - 特定年份特定月份的天数？

Question

如何知道某年某月有多少天？

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

Answer 1

Java 8 及更高版本

@Warren M. Nocos。 如果您尝试使用 Java 8 的新 Date and Time API , 你可以使用 java.time.YearMonth类(class)。见 Oracle Tutorial .

// 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 

Java 7 及更早版本

创建日历，设置年月并使用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

测试:在闰年尝试一个月:

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