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，java上个月, Simp

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，java上个月, Simp

        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,1);//设置为1号,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));     }