另一正则表达式需求：生成符合指定规则的正则表达式

Let's craft a regex that hits all three of your specified rules, with a clear breakdown so you understand exactly how each part works:

Final Regex #

^(?=.*[A-Za-z])[A-Za-z0-9@'-][A-Za-z0-9@'-\s]*[A-Za-z0-9@'-]$

Component Breakdown #

• ^ & $: Anchor the regex to match the entire string (prevents partial matches from slipping through)
• (?=.*[A-Za-z]): Positive lookahead that guarantees the string includes at least one uppercase or lowercase letter
• [A-Za-z0-9@'-]: Matches the first character (can’t be a space, since space isn’t included here) — covers all allowed non-space characters
• [A-Za-z0-9@'-\s]*: Matches any number of allowed characters in the middle, including spaces (the \s adds space support, * means zero or more occurrences)
• [A-Za-z0-9@'-]: Matches the last character (also can’t be a space, same as the first character)

Valid & Invalid Examples #

• Valid Strings:
  • Jane-Smith
  • O'Neil 123
  • admin@test-site
  • X (single letter, meets all rules)
• Invalid Strings:
  • Hello123 (starts with space)
  • Hello123 (ends with space)
  • 123-@ (no letters included)
  • Hello!World (contains exclamation mark, not in allowed character set)

Quick Notes #

• If you’re using this regex in a language that requires backslash escaping (like Java), you’ll need to double the backslash for \s, making it \\s
• The hyphen (-) is placed at the end of the character set to avoid being interpreted as a range (e.g., a-z), keeping it safe and readable

内容的提问来源于stack exchange，提问作者Ionut Cirja