获得某个月的天数(java,oracle,mysql)

java方式：

Calendar cal = Calendar.getInstance();

cal.set(Calendar.YEAR,year);

cal.set(Calendar.MONTH,month+1);//2月

int maxDate = cal.getActualMaximum(Calendar.DATE);

mysql方式：

"SELECT day(LAST_DAY(‘2007-04-01'));";

oracle方式：

select to_number(add_months(to_date('2007-04','yyyy-fmmm'),1)-to_date(’2007-04','yyyy-fmmm')) daynum from dual