18Mar

jsp中的日期问题及其它

Posted in 所谓技术 by gleon

日期问题
1、获取服务器端当前日期：

  1. <!--page import="java.util.Date-->
  2. <!--r>   Date myDate = new Date();
  3. -->

输出结果：
引用
Fri Jan 05 21:39:40 CST 2007
2、获取当前年、月、日：

  1. <!--page import="java.util.Date-->
  2.  
  3. <!--r>   Date myDate = new Date();
  4. int thisYear = myDate.getYear() + 1900;
  5. int thisMonth = myDate.getMonth() + 1;
  6. int thisDate = myDate.getDate();
  7. -->

输出结果：
引用
2007 1 5
3、按本地时区输出当前日期

  1. <!--page import="java.util.Date-->
  2. <!--r>   Date myDate = new Date();
  3. out.println(myDate.toLocaleString());
  4. -->

结果：2007-1-5 21:43:27

4、获取数据库中字段名为”publish_time“、类型为Datetime的值

  1. <!--page import="java.util.Date-->
  2. <!--r>   ...连接数据库...
  3. ResultSet rs = ...
  4. Date sDate = rs.getDate("publish_time");
  5. -->

5、按照指定格式打印日期

  1. <!--page import="java.util.Date-->
  2. <!--page import="java.text.DateFormat-->
  3. <!--r>   Date dNow = new Date();
  4.  
  5. SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz");
  6. out.println("It is " + formatter.format(dNow));
  7. -->

输出的结果为：
It is 星期五 2007.01.05 at 21:43:27 下午 CST
6、将字符串转换为日期

  1. <!--page import="java.util.Date-->
  2. <!--page import="java.text.DateFormat-->
  3. <!--r>   String input = "1222-11-11";
  4. SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  5. Date t = null;
  6. try{
  7. t = formatter.parse(input);
  8. out.println(t);
  9. }catch(ParseException e){
  10. out.println("unparseable using " + formatter);
  11. }
  12. -->

输出结果为：
Fri Nov 11 00:00:00 CST 1222
7、计算日期之间的间隔

  1. <!--page import="java.util.Date-->
  2. <!--page import="java.text.DateFormat-->
  3. <!--r>   String input = "2003-05-01";
  4. SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  5. Date d1 = null;
  6. try{
  7. d1 = formatter.parse(input);
  8. }catch(ParseException e){
  9. out.println("unparseable using " + formatter);
  10. }
  11.  
  12. Date d2 = new Date();
  13.  
  14. long diff = d2.getTime() - d1.getTime();
  15. out.println("Difference is " + (diff/(1000*60*60*24)) + " days.");
  16. -->

输出结果为：
Difference is 29 days.

8、日期的加减运算
方法：用Calendar类的add()方法

  1. <!--page import="java.util.*-->
  2. <!--page import="java.text.*-->
  3. <!--r>   Calendar now = Calendar.getInstance();
  4. SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz");
  5. out.println("It is now " + formatter.format(now.getTime()));
  6. now.add(Calendar.DAY_OF_YEAR,-(365*2));
  7. out.println("
  8. ");
  9. out.println("Two years ago was " + formatter.format(now.getTime()));
  10. -->

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

  1. <!--page import="java.util.*-->
  2. <!--page import="java.text.*-->
  3. <!--r>   DateFormat df = new SimpleDateFormat("yyy-MM-dd");
  4. Date d1 = df.parse("2000-01-01");
  5. Date d2 = df.parse("1999-12-31");
  6.  
  7. String relation = null;
  8. if(d1.equals(d2))
  9. relation = "the same date as";
  10. else if(d1.before(d2))
  11. relation = "before";
  12. else
  13. relation = "after";
  14. out.println(d1 +" is " + relation + ' ' + d2);
  15. -->

输出结果为：

  1. 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

  1. <!--page import="java.text.*-->
  2. <!--r>   long t0,t1;
  3. t0 = System.currentTimeMillis();
  4. out.println("Cyc starts at " + t0);
  5. int k = 0;
  6. for(int i =0;i<100000;i++){
  7. k += i;
  8. }
  9. t1 = System.currentTimeMillis();
  10. out.println("
  11. ");
  12. out.println("Cyc ends at " + t1);
  13. out.println("
  14. ");
  15. out.println("This run took " + (t1-t0) + "ms.");
  16. -->

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

其它：如何格式化小数


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