Java 正则表达式精确匹配字符串？

Regular Expression to Match String Exactly?

提问by Craig Otis

I'll preface this question by mentioning that while I'm far from a regular expressions guru, they are not completely foreign to me. Building a regular expression to search for a pattern inside a particular string generally isn't a problem for me, but I have a (maybe?) unique situation.

我将在这个问题的开头提到，虽然我离正则表达式大师还很远，但它们对我来说并不完全陌生。构建正则表达式来搜索特定字符串中的模式通常对我来说不是问题，但我有一个（也许？）独特的情况。

I have a set of values, say:

我有一组值，比如：

028938
DEF567987
390987.456
GHI345928.039

028938
DEF567987
390987.456
GHI345928.039

I want to match a certain set of strings, such as:

我想匹配一组特定的字符串，例如：

• Strings composed of exactly 6 digits
• Strings composed of exactly 6 digits, a decimal, followed by exactly 3 more digits

• 由 6 位数字组成的字符串
• 由 6 位数字组成的字符串，一个小数，后跟 3 位数字

In the above examples, the first and third values should be matched.

在上面的例子中，第一个和第三个值应该匹配。

I'm using the regular expressions:

我正在使用正则表达式：

[0-9]{6}
[0-9]{6}.[0-9]{3}

Unfortunately, since all the above examples containthe specified pattern, all values are matched. This is not my intention.

不幸的是，由于上述所有示例都包含指定的模式，因此所有值都匹配。这不是我的本意。

So my question, in a nutshell, is how to write a regular expression that matches a string exactly and completely, with no additional characters to the right or left of the matched pattern? Is there a term for this type of matching? (Google was no help.) TIA

所以我的问题，简而言之，是如何编写一个与字符串完全匹配的正则表达式，在匹配模式的右侧或左侧没有额外的字符？这种类型的匹配有术语吗？（谷歌没有帮助。）TIA

采纳答案by CaffGeek

use ^and $to match the start and end of your string

使用^and$匹配字符串的开头和结尾

^[0-9]{6}$
^[0-9]{6}\.[0-9]{3}$

Reference: http://www.regular-expressions.info/anchors.html

参考：http: //www.regular-expressions.info/anchors.html

Also, as noted by Mikael Svenson, you can use the word boundary \bif you are searching for this pattern in a larger chunk of text.

此外，正如 Mikael Svenson 所指出的，\b如果您要在更大的文本块中搜索此模式，则可以使用单词边界。

Reference: http://www.regular-expressions.info/wordboundaries.html

参考：http: //www.regular-expressions.info/wordboundaries.html

You could also write both those regexes in one shot

你也可以一次写出这两个正则表达式

^\d{6}(\.\d{3})?$

回答by Mikael Svenson

You can use ^to require the matching at the start of a line and $to require the end of a line

您可以使用^要求在行首匹配并$要求在行尾匹配

^[0-9]{6}\.[0-9]{3}$

[0-9] can also be written as \d

[0-9] 也可以写成 \d

^\d{6}\.\d{3}$

You can also use \bfor word boundaries if you want to match your pattern in a line with eg. spaces in them

\b如果您想在一行中匹配您的模式，您也可以用于单词边界，例如。其中的空间

\btest\b

will match the word testin this line

将匹配test此行中的单词

this is a test for matching

回答by Mikael Svenson

^\d{6}$
^\d{6}\.\d{3}$

are the correct patterns you can test them 6 digits onlyand 6 digits dot 3 digits.

是正确的模式，您可以仅测试6 位数字和6 位数字点 3 位数字。

^\d{6}((\.\d{3}$)|$)

will match either 6 digits or 6 digits dot 3 digits

将匹配6 位数字或 6 位数字点 3 位数字

Rubularis your friend!

Rubular是你的朋友！

回答by Gopi

Match this regex:

匹配这个正则表达式：

"^\d{6}((\.\d{3}$)|$)"

回答by Ryan Conrad

i think you want something like this:

我想你想要这样的东西：

"^\d{6}(\.\d{3})?$"

you need to escape the "dot" as it is "any" character in regexp.

您需要转义“点”，因为它是正则表达式中的“任何”字符。