我想解析一个正则表达式。
有没有一种方法可以检查下面的正则表达式的含义:
^(PC([Y\\d])|GC([Y\\d])|Y|\\d)\\d{4,5}$
你可以使用Regular Expression Analyzer或Debuggex来分析正则表达式。
^ = start of string
() = capturing groups
[] = character classes
\d = digit in 0-9
\\ = literal backslash
| = OR
{} = count of leading item
$ = end of string
^(PC([Y\\d])|GC([Y\\d])|Y|\\d)\\d{4,5}$
1. ^ - Beginning of line
2. ( - Beginning of a capture group
3. PC - Finds `PC` exactly
4. ([Y\\d]) - Creates a capture group for a Y or a single digit (0-9)
5. | - This is an OR statement
6. GC - Finds `GC` exactly
7. ([Y\\d]) - Same as 4
8. | - This is an OR statement
9. Y - Finds `Y` exactly
10. | - This is an OR statement
11. \\d - This looks for a single digit (0-9)
12. ) - End of capture group. Lines 3-11 will be in this capture group
13. \\d{4,5} - This will look any digit exactly 4 or 5 times
14. $ - End of line
这里有3个捕获组:
1. (PC([Y\\d])|GC([Y\\d])|Y|\\d)
2. ([Y\\d]) (The first one)
3. ([Y\\d]) (The second one)
\
的原因是为了转义Java中的 \
。并非所有语言都需要这样做,据我所知,有些语言需要3个。如果您注意到上面的RegExr,我已经将它们删除,以便RegExr能够正确解析正则表达式。