Collections 最大值，最小值

 for(RoomBillSysRoomCrmGuest roomBillSysRoomCrmGuest : roomBillSysRoomCrmGuests){                  Date inDate = roomBillSysRoomCrmGuest.getCheckInTime();                  checkInTimes.add(inDate.getTime());                  Date outDate = roomBillSysRoomCrmGuest.getCheckOutTime();                  checkOutTimes.add(outDate.getTime());              }              Long minNumber =  Collections.min(checkInTimes);              Long manNumber =  Collections.max(checkOutTimes);