SimpleDateFormat的线程安全问题与解决方案

 1 public class DateUtil {
 2 
 3     static final DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 4 
 5     static ThreadLocal<DateFormat> threadLocal = new ThreadLocal<DateFormat>() {
 6         protected DateFormat initialValue() {
 7             return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 8         }
 9     };
10 
11     private static DateFormat dateFormat() {
12         // return sdf;
13         return threadLocal.get();
14     }
15 
16     public static Date parse(String dateStr) throws ParseException {
17         return dateFormat().parse(dateStr);
18     }
19 
20     public static String format(Date date) {
21         return dateFormat().format(date);
22     }
23 
24     public static void main(String[] args) {
25         for (int i = 0; i < 3; i++) {
26             new Thread() {
27                 public void run() {
28                     while (true) {
29                         try {
30                             Thread.sleep(2000);
31                         } catch (InterruptedException e1) {
32                             e1.printStackTrace();
33                         }
34                         
35                         try {
36                             System.out.println(this.getName() + ":" + DateUtil.parse("2013-05-24 06:02:20"));
37                         } catch (ParseException e) {
38                             e.printStackTrace();
39                         }
40                     }
41                 }
42             }.start();
43         }
44     }