Java正则表达式错误 - 后瞻组没有明显的最大长度 [英] Java regex error - Look-behind group does not have an obvious maximum length

问题描述

我收到此错误：

java.util.regex.PatternSyntaxException: Look-behind group does not have an
    obvious maximum length near index 22
([a-z])(?!.*\1)(?<!\1.+)([a-z])(?!.*\2)(?<!\2.+)(.)(\3)(.)(\5)
                      ^

我正在尝试匹配 COFFEE ，但不是 BOBBEE 。

I'm trying to match COFFEE, but not BOBBEE.

我正在使用java 1.6。

I'm using java 1.6.

推荐答案

Java没有' t支持后面的可变长度。

在这种情况下，你似乎可以轻易忽略它（假设你的整个输入是一个单词）：

Java doesn't support variable length in look behind.
In this case, it seems you can easily ignore it (assuming your entire input is one word):

([a-z])(?!.*\1)([a-z])(?!.*\2)(.)(\3)(.)(\5)

两个lookbehinds都不添加任何东西：第一个断言至少两个字符只有你有一个，第二个检查第二个字符与第一个字符不同，已经被覆盖（？！。* \\ 1）。

Both lookbehinds do not add anything: the first asserts at least two characters where you only had one, and the second checks the second character is different from the first, which was already covered by (?!.*\1).

工作示例： http://regexr.com?2up96

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