Date 与 Calendar 计算时间及天数

   有时我们会比较时间，例如：7天前，7天后。

   虽然是基础，但好久没写基层代码了，今天贴一个demo.

1：方案1

		Calendar c = Calendar.getInstance();
		int year = c.get(Calendar.YEAR);
		int month = c.get(Calendar.MONTH)+1;
		int date = c.get(Calendar.DATE);
		int num = c.get(Calendar.DAY_OF_YEAR);
		
		System.out.println(year +"_"+ month+"_"+date+"是今年的第"+num+"天");
		
		Calendar cal = new GregorianCalendar();
		String a = "2011-03-02 10:11:52";
		SimpleDateFormat  sf = new SimpleDateFormat("yyyy-MM-dd mm:hh:ss");
		Date d;
		try {
			d = sf.parse(a);
			cal.setTime(d);
		} catch (ParseException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		int year1 = cal.get(Calendar.YEAR);
		int month1 = cal.get(Calendar.MONTH)+1;
		int date1 = cal.get(Calendar.DATE);
		int num1 = cal.get(Calendar.DAY_OF_YEAR);		
		System.out.println(year1 +"_"+ month1+"_"+date1+"是今年的第"+num1+"天");

2：方案2:

		int failLoginInterval = 60*60*1000; //1小时
		Date dt = new Date();
		long lastDay = dt.getTime();
		long tmp = lastDay - (failLoginInterval*24*7);


		System.out.println("今天是："+lastDay);
		System.out.println("7天是："+failLoginInterval*24*7);
		System.out.println("七天前："+tmp);

会话不多说了。此处贴代码，由于时间有限。