// 獲取當月第一天和最后一天
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
String firstday, lastday;
Calendar cale = Calendar.getInstance();
cale.add(Calendar.MONTH, 0);
cale.set(Calendar.DAY_OF_MONTH, 1);
firstday = format.format(cale.getTime());
// 獲取前月的最后一天
cale = Calendar.getInstance();
cale.add(Calendar.MONTH, 1);
cale.set(Calendar.DAY_OF_MONTH, 0);
lastday = format.format(cale.getTime());
System.out.println("本月第一天和最后一天分別是 ： " + firstday + " and " + lastday);