我怎样才能得到一个正则表达式来检查一个字符串只包含字母字符[A-Z]或[A-Z]？ [英] How can I get a regex to check that a string only contains alpha characters [a-z] or [A-Z]?

问题描述

我试图创建一个正则表达式来验证一个给定的字符串只有字母字符a-z或A-Z。该字符串可长达25个字母。 （我不知道，如果正则表达式可以检查字符串的长度）

例子：

1 ABCDEF=真;

2 a2bdef= FALSE ;

3 333= FALSE;

4 J=真;

5 aaaaaaaaaaaaaaaaaaaaaaaaaa= FALSE; // 26个字母

下面是我迄今为止...无法弄清楚什么是错了，但

正则表达式alphaPattern =新的正则表达式（[^ A-Z] | [^ A-Z]）;

我想这将意味着该字符串可以包含A-Z只有大写或小写字母，但是当我把它匹配所有的字母返回false字符串...

此外，关于使用正则表达式与其他验证方法将会大大AP preciated效率的任何建议。

解决方案

 正则表达式lettersOnly =新的正则表达式（^ [A-ZA-Z] {1,25} $）;
 

• ^ 表示开始于字符串开始匹配


• [A-ZA-Z] 表示匹配小写和大写字母A-Z


• {1,25} 表示匹配previous项目（字符类，见上文）1至25倍


• $ 表示只有当光标在字符串结尾匹配

I'm trying to create a regex to verify that a given string only has alpha characters a-z or A-Z. The string can be up to 25 letters long. (I'm not sure if regex can check length of strings)

Examples:
1. "abcdef" = true;
2. "a2bdef" = false;
3. "333" = false;
4. "j" = true;
5. "aaaaaaaaaaaaaaaaaaaaaaaaaa" = false; //26 letters

Here is what I have so far... can't figure out what's wrong with it though

Regex alphaPattern = new Regex("[^a-z]|[^A-Z]");

I would think that would mean that the string could contain only upper or lower case letters from a-z, but when I match it to a string with all letters it returns false...

Also, any suggestions regarding efficiency of using regex vs. other verifying methods would be greatly appreciated.

解决方案

Regex lettersOnly = new Regex("^[a-zA-Z]{1,25}$");

• ^ means "begin matching at start of string"
• [a-zA-Z] means "match lower case and upper case letters a-z"
• {1,25} means "match the previous item (the character class, see above) 1 to 25 times"
• $ means "only match if cursor is at end of string"

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