java 獲取指定月份第一天和最后一天

第一天

public static String getFisrtDayOfMonth(int year,int month)
    {
        Calendar cal = Calendar.getInstance();
        //設置年份
        cal.set(Calendar.YEAR,year);
        //設置月份
        cal.set(Calendar.MONTH, month-1);
        //獲取某月最小天數
        int firstDay = cal.getActualMinimum(Calendar.DAY_OF_MONTH);
        //設置日歷中月份的最小天數
        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());
        return firstDayOfMonth;
    }

最后一天

public static String getLastDayOfMonth(int year,int month)
    {
        Calendar cal = Calendar.getInstance();
        //設置年份
        cal.set(Calendar.YEAR,year);
        //設置月份
        cal.set(Calendar.MONTH, month-1);
        //獲取某月最大天數
        int lastDay = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
        //設置日歷中月份的最大天數
        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());
        return lastDayOfMonth;
    }