Java正则表达式String.matches工作不一致(Java regex String.matches working inconsistently)

 我有一个正则表达式来检查一个字符串是否是一个数字。 格式的千位分隔符是一个空格，小数点分隔符是一个点。 小数点后部分是可选的。 
 
 问题是，在某些时候String.matches（）函数停止按预期工作。 之前的工作，不再工作。 
 
 例如，JUnit代码： 
 
import junit.framework.Assert;
import org.junit.Test;

public class RegExTest {

    @Test
    public void testThousandSeperatorRegex()
    {
        String regEx = "([0-9]{1,3}( [0-9]{3})*(\\.[0-9]+)?|\\.[0-9]+)";
        Assert.assertEquals(true, "1".matches(regEx));
        Assert.assertEquals(true, "10".matches(regEx));
        Assert.assertEquals(true, "100".matches(regEx));
        Assert.assertEquals(true, "1 000".matches(regEx));
        Assert.assertEquals(true, "10 000".matches(regEx));
        Assert.assertEquals(true, "100 000".matches(regEx));
        Assert.assertEquals(true, "1 000 000".matches(regEx));
        Assert.assertEquals(true, "10 000 000".matches(regEx));
        Assert.assertEquals(false, "10000.56".matches(regEx));
        Assert.assertEquals(true, "8 734".matches(regEx));
    }
}
 
 “8 734”的最后一行失败。 当我用“1 000”代替它时，它仍然会失败。 最后，同一次运行中的相同代码在第四行断言中传递，但最后一次失败（新代码保存！）。 但有时候，一切都开始按预期工作，直到......再次失败。 所以我想这将很难重现我的问题。 也许还有一些我做错的事情我没有注意到，因此没有被描述，但我试图尽可能地说明问题。 这个让我很困惑。 String.matches（）是否有内存或什么？ 
 
 正则表达式可能有问题吗？ 我正在跳过^$因为String.matches无论如何都可以在整个字符串上工作。 我已经尝试过java.util.regex和jregex包，问题依然存在。 
 
 我正在使用JDK 6u31。 
 
 任何想法赞赏。 
 
 UPD：好的，在发布这个Q之后，代码开始工作并且至今没有失败。 也许这是与我有关的事情，但自从上周以来，这一直困扰着我，我已经能够一次又一次地复制它。 我会继续使用我的代码，如果它能继续工作，我会解决这个问题。 此外，我会尝试确定究竟是什么造成了这个问题。 同时，如果有人遇到同样的问题，请分享您的知识。 否则，这看起来像一个问题，可以通过知识解决，而不是通过调试。 为了捍卫自己的愚蠢，我可以说我已经编程了很多年，这是论坛上的第一篇文章:)。 到现在为止，我能够通过调试，阅读文档和搜索其他Q的论坛来解决我的问题。 

I have a regex which checks if a string is a number. The format's thousand separator is a white space, decimal separator is a dot. After-decimal part is optional.
 
The issue is that at some point String.matches() function stops working as expected. What worked before, does not work anymore.
 
For example, JUnit code:
 
import junit.framework.Assert;
import org.junit.Test;

public class RegExTest {

    @Test
    public void testThousandSeperatorRegex()
    {
        String regEx = "([0-9]{1,3}( [0-9]{3})*(\\.[0-9]+)?|\\.[0-9]+)";
        Assert.assertEquals(true, "1".matches(regEx));
        Assert.assertEquals(true, "10".matches(regEx));
        Assert.assertEquals(true, "100".matches(regEx));
        Assert.assertEquals(true, "1 000".matches(regEx));
        Assert.assertEquals(true, "10 000".matches(regEx));
        Assert.assertEquals(true, "100 000".matches(regEx));
        Assert.assertEquals(true, "1 000 000".matches(regEx));
        Assert.assertEquals(true, "10 000 000".matches(regEx));
        Assert.assertEquals(false, "10000.56".matches(regEx));
        Assert.assertEquals(true, "8 734".matches(regEx));
    }
}
 
The last line with "8 734" fails. When I replace it with "1 000" it continues to fail. Eventually, the same code at the same run passes in the 4th line of assertions, but fails in the last (the new code is saved!). But there are times when everything starts working just as expected until.. start failing again. So I suppose that it will be hard to reproduce my issue. Maybe there are something else that I'm doing wrong which I haven't noticed and thus described, but I tried to make it as plain as possible. This one confuses me a lot. Does String.matches() has a memory or what?
 
Could there be something wrong with the regular expression? I'm skipping ^$ as String.matches works on whole string anyway. I have tried java.util.regex and jregex packages, the issue persisted.
 
I'm using JDK 6u31.
 
Any ideas appreciated.
 
UPD: ok, after posting this Q the code started to work and hasn't fail so far. Maybe it was something with me, but this has bothered me since last week and I have been able to replicate it again and again. I will continue with my piece of code and if it will continue to work I will close this issue. Also I will try to determine what exactly caused the problem. Meanwhile, if there are someone out there who has encountered the same issue, please share your knowledge. Otherwise, this looks like an issue that can be solved by knowledge, not by debugging. To defend myself from stupidity I can say I have been programming for many years and this is the 1st ever post in forums :). Until now I was able to solve my problems with debugging, reading docs and searching forums of other Qs. 

原文：https://stackoverflow.com/questions/10126347