日期操作类

  /**
	 * 日期加减n天
	 */
	private static Date dateAddSubNDay(Date date, char ch, int n)
	{
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(date);

		if (ch == '+')
		{
			calendar.set(Calendar.DAY_OF_YEAR, calendar
					.get(Calendar.DAY_OF_YEAR) + n);
		}
		else if (ch == '-')
		{
			calendar.set(Calendar.DAY_OF_YEAR, calendar
					.get(Calendar.DAY_OF_YEAR) - n);
		}

		return calendar.getTime();
	}
	
	/**
	 * 月份加减n天
	 */
	public static Date dateAddSubNMonth(String date, char ch, int n)
	{
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(strToDate(date, "yyyy-MM-dd"));

		if (ch == '+')
		{
			calendar.set(Calendar.MONTH, calendar
					.get(Calendar.MONTH) + n);
		}
		else if (ch == '-')
		{
			calendar.set(Calendar.MONTH, calendar
					.get(Calendar.MONTH) - n);
		}

		return calendar.getTime();
	}

	/**
	 * 根据年月日得到星期 1 - 7
	 */
	public static int getWeek(int y, int m, int d)
	{
		//用来保存计算得到的星期几的整数
		int a = 7; 
		int int_date = -1;
		//如果是一月或二月进行换算
		if ((m == 1) || (m == 2))
		{
			m += 12;
			y--;
		}
		//得到的星期几的整数
		a = (d + 2 * m + 3 * (m + 1) / 5 + y + y / 4 - y / 100 + y / 400) % 7; 
		switch (a)
		{
			case 0:
				int_date = 1;
				break;
			case 1:
				int_date = 2;
				break;
			case 2:
				int_date = 3;
				break;
			case 3:
				int_date = 4;
				break;
			case 4:
				int_date = 5;
				break;
			case 5:
				int_date = 6;
				break;
			case 6:
				int_date = 7;
				break;
		}
		return int_date;
	}
	
	/**
	 * 计算两个日期相差月份
	 */
	public static final int getMonths(String d1, String d2)    
  {    
		Date date1 = strToDate(d1, "yyyy-MM-dd");
		Date date2 = strToDate(d2, "yyyy-MM-dd");
		int month = 12*(date1.getYear()-date2.getYear())+date1.getMonth()-date2.getMonth();
		return month;
  }   
    
    
   /**
	 * 得到某个月的最后一日日期
	 */
	public static String getCurrMonthEndDate(int year, int month, int day)
	{
				Calendar cal = Calendar.getInstance(); //日历 
        // 当前月＋1，即下个月 
				cal.set(year, month - 1, day);
		
        cal.add(cal.MONTH, 1); //得到下个月的月份 
        
        // 将下个月1号作为日期初始zhii 
        cal.set(cal.DATE, 1); 
        
        // 下个月1号减去一天，即得到当前月最后一天 
        cal.add(cal.DATE, -1); 
        
        java.text.SimpleDateFormat df = new java.text.SimpleDateFormat( 
                "yyyy-MM-dd"); 
        
        String day_end = df.format(cal.getTime()); 
        
        return day_end;
	}