获取月份的第一天和最后一天

1:获得该月最一天

  public static String getFirstDayOfMonth(int year, int month) {
        Calendar cal = Calendar.getInstance();
        // 设置月份
        cal.set(Calendar.YEAR, year);
        cal.set(Calendar.MONTH, month - 1);
        // 获取某月最小天数
        int firstDay = cal.getActualMinimum(Calendar.DAY_OF_MONTH);
        // 设置日历中月份的最小天数
        cal.set(Calendar.DAY_OF_MONTH, firstDay);
        // 格式化日期
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String firstDayOfMonth = sdf.format(cal.getTime()) + " 00:00:00";
        return firstDayOfMonth;
    }

2:获得该月最后一天

/**
     * 获得该月最后一天
     * 
     * @param year
     * @param month
     * @return
     */
    public static String getLastDayOfMonth(int year, int month) {
        Calendar cal = Calendar.getInstance();
        // 设置月份
        cal.set(Calendar.YEAR, year);
        cal.set(Calendar.MONTH, month - 1);
        // 获取某月最大天数
        int lastDay = 0;
        // 2月的平年瑞年天数
        if (month == 2) {
            lastDay = cal.getLeastMaximum(Calendar.DAY_OF_MONTH);
        } else {
            lastDay = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
        }
        // 设置日历中月份的最大天数
        cal.set(Calendar.DAY_OF_MONTH, lastDay);
        // 格式化日期
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String lastDayOfMonth = sdf.format(cal.getTime()) + " 23:59:59";
        return lastDayOfMonth;
    }