java.text.SimpleDateFormat多线程下的问题

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1. 今天在做性能压测的时候发现java.text.SimpleDateFormat多线程下的错误

2. 先贴出两段错误大家看一下：

Exception in thread "pool-1-thread-42" java.lang.NumberFormatException: multiple points      at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1084)      at java.lang.Double.parseDouble(Double.java:510)      at java.text.DigitList.getDouble(DigitList.java:151)      at java.text.DecimalFormat.parse(DecimalFormat.java:1303)      at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1591)      at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1312)      at java.text.DateFormat.parse(DateFormat.java:335)      at infoair.obcs.utilities.DateTimeUtils.validateDateTime(DateTimeUtils.java:294)      at infoair.obcs.utilities.TestThread.run(DateTimeUtils.java:318)      at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)      at java.lang.Thread.run(Thread.java:619)

Exception in thread "pool-1-thread-9" java.lang.NumberFormatException: For input string: ""      at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)      at java.lang.Long.parseLong(Long.java:431)      at java.lang.Long.parseLong(Long.java:468)      at java.text.DigitList.getLong(DigitList.java:177)      at java.text.DecimalFormat.parse(DecimalFormat.java:1298)      at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1591)      at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1312)      at java.text.DateFormat.parse(DateFormat.java:335)      at infoair.obcs.utilities.DateTimeUtils.validateDateTime(DateTimeUtils.java:294)      at infoair.obcs.utilities.TestThread.run(DateTimeUtils.java:318)      at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)      at java.lang.Thread.run(Thread.java:619)

分析：自己在本地debug的时候没有任何问题，但是线上很奇怪。然后查看jdk文档发现这个类不是线程安全的。

Date formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.

解决方案：

在调用的代码中每次new一个就可以了。

参考：http://stackoverflow.com/questions/4021151/java-dateformat-is-not-threadsafe-what-does-this-leads-to

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