JAVA Calendar 获取上个月、当前月的第一天和最后一天时间

SimpleDateFormat df =new SimpleDateFormat("yyyyMMdd");

//获取上个月第一天时间 ，当前月减去1获取上月月份，获取第一天日期

Calendar calendar = Calendar.getInstance();

calendar.add(Calendar.MONTH, -1);

calendar.set(Calendar.DAY_OF_MONTH, 1);

String berforeFirstDay = df.format(calendar.getTime());

//获取当前月第一天日期，减去一天，获取上个月最后一天时间 

Calendar calendar1 = Calendar.getInstance();

calendar1.set(Calendar.DAY_OF_MONTH, 1);

calendar1.add(Calendar.DATE, -1);

String berforeLastDay = df.format(calendar1.getTime());

//获取当前月第一天时间 

Calendar calendar2 = Calendar.getInstance();

calendar2.set(Calendar.DAY_OF_MONTH, 1);

String firstDay = df.format(calendar2.getTime());

//先获取下个月第一天日期，减去一天，获取当前月最后一天时间

Calendar calendar3 = Calendar.getInstance();

calendar3.add(Calendar.MONTH, 1);

calendar3.set(Calendar.DAY_OF_MONTH, 1);

calendar3.add(Calendar.DATE, -1);

String lastDay = df.format(calendar3.getTime());