Java怎么得到上一月有多少天

Calendar cal = Calendar.getInstance();
cal.set(Calendar.YEAR,2010);
cal.set(Calendar.MONTH, 6);//Java月份才0开始算 6代表上一个月7月
int dateOfMonth = cal.getActualMaximum(Calendar.DATE);

Calendar c=Calendar.getInstance();
c.set(Calendar.DAY_OF_MONTH,1);//设置为当前月第一天
c.add(Calendar.DAY_OF_MONTH, -1);//-1天得到上月最后一天

System.out.println(c.getTime().getDate());

Calendar c = Calendar.getInstance();
System.out.println(c.getActualMaximum(Calendar.DAY_OF_MONTH));
c.set(Calendar.YEAR, 2000);
c.set(Calendar.MONTH, 1); //注意 一月为 0
System.out.println(c.getTime());
System.out.println(c.getActualMaximum(Calendar.DAY_OF_MONTH));