我从来没有真正研究过正则表达式，所以不要真正理解它
我有以下测试电子邮件地址的正则表达式
^([\\w]+)(\\.[\\w]+)*@([\\w\\-]+\\.){1,5}([A-Za-z]){2,4}$
当我输入example@example.cat它失败但当我输入example@example.com它工作......谁能解释这是为什么？
编辑
一直在研究代码，对于上述电子邮件地址，这个正则表达式会失败吗？
^\\w[-._\\w]*\\w@\\w[-._\\w]*\\w\\.\\w{2,6}$
该正则表达式不会失败，.cat但匹配.com您必须有其他问题导致您看到的行为，这是对以下内容的解释regex：
^([\w]+)(\.[\w]+)*@([\w-]+\.){1,5}([A-Za-z]){2,4}$/
^ Start of string
1st Capturing group ([\w]+)
Char class [\w] infinite to 1 times matches one of the following chars: \w
\w Word character [a-zA-Z_\d]
2nd Capturing group (\.[\w]+) infinite to 0 times
\. Literal .
Char class [\w] infinite to 1 times matches one of the following chars: \w
\w Word character [a-zA-Z_\d]
@ Literal @
3rd Capturing group ([\w-]+\.) 5 to 1 times
Char class [\w-] infinite to 1 times matches one of the following chars: \w-
\w Word character [a-zA-Z_\d]
\. Literal .
4th Capturing group ([A-Za-z]) 4 to 2 times
Char class [A-Za-z] matches one of the following chars: A-Za-z
$ End of string
并且第二个也将接受正确的转义（在大多数语言中，双反斜杠会导致两者不匹配）：
/^\w[-._\w]*\w@\w[-._\w]*\w\.\w{2,6}$/
^ Start of string
\w Word character [a-zA-Z_\d]
Char class [-._\w] infinite to 0 times matches one of the following chars: -._\w
\w Word character [a-zA-Z_\d]
\w Word character [a-zA-Z_\d]
@ Literal @
\w Word character [a-zA-Z_\d]
Char class [-._\w] infinite to 0 times matches one of the following chars: -._\w
\w Word character [a-zA-Z_\d]
\w Word character [a-zA-Z_\d]
\. Literal .
\w 6 to 2 times Word character [a-zA-Z_\d]
$ End of string