请注意SimpleDateFormat不是线程安全的

 1 public class TestSimpleDateFormat 
 2 {
 3     final static SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
 4     
 5     public static void main(String[] args) {
 6         
 7         int NUMBER_OF_THREADS = 1000;
 8         
 9         for( int i = 0; i < NUMBER_OF_THREADS ; i++ ) {
10             TimeCalc tc = new TimeCalc("20151212",i);
11             tc.start();
12         }
13     }
14     
15     static class TimeCalc extends Thread {
16         private String date;
17         public String getDate() {
18             return date;
19         }
20         public TimeCalc(String date, int index) {
21             this.date = date;
22         }
23         
24         @Override
25         public void run() {
26             
27             try {
28                 
29                 Date parsedDate = null;
30 //                synchronized(sdf) {
31                     parsedDate = sdf.parse(date);
32 //                }
33                 System.out.println(parsedDate);
34             } catch (ParseException e) {
35                 e.printStackTrace();
36             } catch (Exception e) {
37                 e.printStackTrace();
38             } 
39         }
40         
41     }
42 }

 1     static class MyDateParser extends FastDateParser {
 2 
 3         protected MyDateParser(String arg0, TimeZone arg1, Locale arg2,
 4                 Date arg3) {
 5             super(arg0, arg1, arg2, arg3);
 6         }
 7         
 8         public static MyDateParser getDateParser( String pattern ) {
 9             return new MyDateParser(pattern, TimeZone.getDefault(), Locale.getDefault(), null);
10         }
11         
12     }