日期与字符串转换

港控/mmm° 2022-05-16 05:43 250阅读 0赞

String dateString  = "Tue Apr 15 11:23:55 CST 2014";
    SimpleDateFormat sfEnd = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    SimpleDateFormat sfStart = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy",java.util.Locale.ENGLISH) ;
    System.out.println(sfEnd.format(sfStart.parse(dateString)));

/\*\*  
\* 将字符串类型的时间戳转化为日期字符串  
\* @param timeMillis 如：1497595115014  
\* @return String 如：2017-06-16 14:38:35  
\*/

public static String timeMillisStrToDateStr(String timeMillis){ 
             Date date=new Date(Long.parseLong(timeMillis));
             SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//目标格式
             String dateString = sdf.format(date);
             return dateString;
        }

1、获取服务器端当前日期：

<%@ page import="java.util.Date"%> 
    <% 
    	Date myDate = new Date(); 
    %>

2、获取当前年、月、日：

<%@ page import="java.util.Date"%> 
    
    <% 
    	Date myDate = new Date(); 
    	int thisYear = myDate.getYear() + 1900;//thisYear = 2003 
    	int thisMonth = myDate.getMonth() + 1;//thisMonth = 5 
    	int thisDate = myDate.getDate();//thisDate = 30 
    %>

7、计算日期之间的间隔

<%@ page import="java.util.Date"%> 
    <%@ page import="java.text.DateFormat"%> 
    <% 
    	String input = "2003-05-01"; 
    	SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd"); 
    	Date d1 = null; 
    	try{  
    	d1 = formatter.parse(input); 
    	}catch(ParseException e){  
    	out.println("unparseable using " + formatter); 
    	} 
    	
    	Date d2 = new Date(); 
    	
    	long diff = d2.getTime() - d1.getTime(); 
    	out.println("Difference is " + (diff/(1000*60*60*24)) + " days."); 
    %>

8、日期的加减运算  
方法：用Calendar类的add()方法

<%@ page import="java.util.*"%> 
    <%@ page import="java.text.*"%> 
    <% 
    	Calendar now = Calendar.getInstance(); 
    	SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz"); 
    	out.println("It is now " + formatter.format(now.getTime())); 
    	now.add(Calendar.DAY_OF_YEAR,-(365*2)); 
    	out.println("<br>"); 
    	out.println("Two years ago was " + formatter.format(now.getTime())); 
    %>

输出结果为：  
It is now 星期五 2003.05.30 at 01:45:32 下午 CST  
Two years ago was 星期三 2001.05.30 at 01:45:32 下午 CST

9、比较日期  
方法：用equals()、before()、after()方法

<%@ page import="java.util.*"%> 
    <%@ page import="java.text.*"%> 
    <% 
    	DateFormat df = new SimpleDateFormat("yyy-MM-dd"); 
    	Date d1 = df.parse("2000-01-01"); 
    	Date d2 = df.parse("1999-12-31"); 
    	
    	String relation = null; 
    	if(d1.equals(d2)) 
    	relation = "the same date as"; 
    	else if(d1.before(d2)) 
    	relation = "before"; 
    	else 
    	relation = "after"; 
    	out.println(d1 +" is " + relation + ' ' + d2); 
    %>

输出结果为：  
Sat Jan 01 00:00:00 CST 2000 is after Fri Dec 31 00:00:00 CST 1999

10、记录一件事所花费的时间  
方法：调用两次System.getTimeMillis()方法，求差值

<%@ page import="java.text.*"%> 
    <% 
    	long t0,t1; 
    	t0 = System.currentTimeMillis(); 
    	out.println("Cyc starts at " + t0); 
    	int k = 0; 
    	for(int i =0;i<100000;i++){  
    	k += i; 
    	} 
    	t1 = System.currentTimeMillis(); 
    	out.println("<br>"); 
    	out.println("Cyc ends at " + t1); 
    	out.println("<br>"); 
    	out.println("This run took " + (t1-t0) + "ms."); 
    %>

输出结果为：  
Cyc starts at 1054275312432  
Cyc ends at 1054275312442  
This run took 10ms.

**重点内容\*\*\*\*如何格式化小数**

<%@ page import="java.text.*"%> 
    <% 
    	DecimalFormat df = new DecimalFormat(",###.00"); 
    	double aNumber = 33665448856.6568975; 
    	String result = df.format(aNumber); 
    	out.println(result); 
    %>

输出结果为：  
33,665,448,856.66