获取上一个自然周的 上一个自然月的起始时间范围

一般统计经常用的时间范围，在此提供两个经常用到，时间范围取每个月一号零时至下月一号零时之间例如：当前日期是 0910 0801 00:00:00 —— 0901 00:00:00public static List<Date> getLastMonth(){Calendar calendar = Calendar.getInstance();calendar.set(Calendar.DAY_OF_MONTH,1);//当前月第一天calendar.set(Calendar.HOUR_OF_DAY,0);calendar.set(Calendar.MINUTE,0);calendar.set(Calendar.SECOND,0);Date lastDay = calendar.getTime();calendar.add(Calendar.MONTH,-1);//获取上一个月第一天calendar.set(Calendar.DAY_OF_MONTH,1);Date firstDay = calendar.getTime();List<Date> list = new ArrayList<Date>();list.add(firstDay);list.add(lastDay);return list;}public static List<Date> getLastWeek(){Calendar calendar = Calendar.getInstance();calendar.set(Calendar.DAY_OF_WEEK,2);//当前周第一天，默认每周第一天是周日，所以这里改成每周第二天即周一为第一天calendar.set(Calendar.HOUR_OF_DAY,0);calendar.set(Calendar.MINUTE,0);calendar.set(Calendar.SECOND,0);Date lastDay = calendar.getTime();calendar.add(Calendar.WEEK_OF_MONTH,-1);//获取上一周第一天calendar.set(Calendar.DAY_OF_WEEK,2);Date firstDay = calendar.getTime();List<Date> list = new ArrayList<Date>();list.add(firstDay);list.add(lastDay);return list;}