SimpleDateFormat 未正确解析毫秒
背景：
在我的数据库表中，我有两个时间戳，
timeStamp1 = 2011-08-23 14:57:26.662
timeStamp2 = 2011-08-23 14:57:26.9
当我执行“ORDER BY TIMESTAMP ASC”时，timeStamp2被认为是更大的时间戳（这是正确的）。
要求：我需要获取这些时间戳的差异（timeStamp2 - timeStamp1）
我的实现：
public static String timeDifference(String now, String prev) {
try {
final Date currentParsed = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").parse(now);
final Date previousParsed = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").parse(prev);
long difference = currentParsed.getTime() - previousParsed.getTime();
return "" + difference;
} catch (ParseException e) {
return "Unknown";
}
}
答案应该是238ms，但返回的值是-653ms。 我不确定我做错了什么。有什么建议吗？
Background:
In my database table, I have two timestamps
timeStamp1 = 2011-08-23 14:57:26.662
timeStamp2 = 2011-08-23 14:57:26.9
When I do an "ORDER BY TIMESTAMP ASC", timeStamp2 is considered as the greater timestamp(which is correct).
Requirement: I need to get the difference of these timestamps (timeStamp2 - timeStamp1)
My implementation:
public static String timeDifference(String now, String prev) {
try {
final Date currentParsed = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").parse(now);
final Date previousParsed = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").parse(prev);
long difference = currentParsed.getTime() - previousParsed.getTime();
return "" + difference;
} catch (ParseException e) {
return "Unknown";
}
}
The answer should have been 238ms, but the value that is returned is -653ms.
I'm not sure what I'm doing wrong. Any suggestions?
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评论（4）
您正在解析的格式和使用的格式不匹配。您期望一个三位数字段，但只提供了一位数字。它采用
9并假设您的意思是009，而您想要的是900。日期格式很复杂，当您以不同的格式证明日期时，它可能会以不同的方式解析它们。文档说
S表示毫秒数，该字段中的数字是 9，因此它的行为正确。编辑：这个例子可能有助于
打印
The format you are parsing and the format uses doesn't match. You expect a three digit field and are only providing one digits. It takes
9and assumes you mean009when what you want is900. Date formats are complicated and when you prove dates in a different format it may parse them differently to you.The documentation says
Smeans the number of milli-seconds and the number in that field is 9, so it is behaving correctly.EDIT: This example may help
prints
我不完全确定，但 JavaDoc 指出了这一点：
这表示
2011-08-23 14:57:26.9中的毫秒将被解析为9而不是900。添加尾随零可能有效：2011-08-23 14:57:26.900。I'm not entirely sure, but the JavaDoc states this:
This indicates that the milliseconds from
2011-08-23 14:57:26.9would be parsed as9instead of900. Adding the trailing zeros might work:2011-08-23 14:57:26.900.我建议使用 Joda-Time。它可以正确处理这些情况。在以下示例中，毫秒被正确解析为 200ms。
I'd suggest using Joda-Time. It handles these situations properly. In the following example, the milliseconds are correctly parsed as 200ms.
我也遇到了同样的问题，日志文件中的时间太准确，只有 6 位数毫秒。解析时间相差高达 16 分钟！搞什么？
更改位数减少了错误的差异，并且多亏了这个线程，我可以识别问题：
由于
SimpleDateFormat内部仅处理 3 位数字，我用一个小正则表达式删除了不必要的数字（忽略舍入错误，工作1 最多 n 位）：感谢@Peter Lawrey 的回答，防止我发疯:-)
I had the same problem with too accurate time from my logfiles with 6 digit milliseconds. Parsing Time gave up to 16 minutes difference! WTF?
Changing the number of digits reduced the erroneous difference and thanks to this thread I could identify the problem:
As
SimpleDateFormatinternally handles only 3 digits I removed the unnecessary with a small regex (ignoring round-off errors, working for 1 up to n digits):Thanks to @Peter Lawrey for your answer, prevented me going insane :-)