java获取当前月第一天和最后一天，上个月第一天和最后一天

????????SimpleDateFormat?format?=?new?SimpleDateFormat("yyyy-MM-dd");?
?????????
????????//获取前月的第一天
????????Calendar???cal_1=Calendar.getInstance();//获取当前日期?
????????cal_1.add(Calendar.MONTH,?-1);
????????cal_1.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天?
????????firstDay?=?format.format(cal_1.getTime());
????????System.out.println("-----1------firstDay:"+firstDay);
????????//获取前月的最后一天
????????Calendar?cale?=?Calendar.getInstance();???
????????cale.set(Calendar.DAY_OF_MONTH,0);//设置为1号,当前日期既为本月第一天?
????????lastDay?=?format.format(cale.getTime());
????????System.out.println("-----2------lastDay:"+lastDay);
?????????
?????????
????????//获取当前月第一天：
????????Calendar?c?=?Calendar.getInstance();????
????????c.add(Calendar.MONTH,?0);
????????c.set(Calendar.DAY_OF_MONTH,当前日期既为本月第一天?
????????String?first?=?format.format(c.getTime());
????????System.out.println("===============first:"+first);
?????????
????????//获取当前月最后一天
????????Calendar?ca?=?Calendar.getInstance();????
????????ca.set(Calendar.DAY_OF_MONTH,?ca.getActualMaximum(Calendar.DAY_OF_MONTH));??
????????String?last?=?format.format(ca.getTime());
????????System.out.println("===============last:"+last);
????????
????????/**?
	?*?字符串的日期格式的计算?
	?*/?
	public?static?int?daysBetween(String?smdate,String?bdate)?throws?ParseException{?
????	????SimpleDateFormat?sdf=new?SimpleDateFormat("yyyy-MM-dd");?
????	????Calendar?cal?=?Calendar.getInstance();?
????	????cal.setTime(sdf.parse(smdate));?
????	????long?time1?=?cal.getTimeInMillis();?
????	????cal.setTime(sdf.parse(bdate));?
????	????long?time2?=?cal.getTimeInMillis();?
????	????long?between_days=(time2-time1)/(1000*3600*24);?
????	????return?Integer.parseInt(String.valueOf(between_days));?
	}