java 获取某年某月的最后一天和第一天

Posted 2021-05-07

public static String getFirstAndLastDay(int year, int month) {
    	String firstAndLastDay = "";
		if(year < 0 || month < 1) {
			return "fail";
		}
		Calendar cal = Calendar.getInstance();
		cal.set(Calendar.YEAR, year);
		//Calendar月份从0开始
		cal.set(Calendar.MONTH, month - 1);
		//方便查看
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
		//获取year年month月的开始一天
		int firstDay = cal.getActualMinimum(Calendar.DAY_OF_MONTH);
		//设置Calendar为指定月份的第一天
		cal.set(Calendar.DAY_OF_MONTH, firstDay);
		//指定月份第一天
		firstAndLastDay += sdf.format(cal.getTime())+";";
		
		//指定月份最后一天
		int lastDay = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
		cal.set(Calendar.DAY_OF_MONTH, lastDay);
		firstAndLastDay += sdf.format(cal.getTime());
		
		return firstAndLastDay;
	}