java - 删除 Re : Fwd: from Mail subjects

Question

我正在尝试建立一个正则表达式来从邮件主题中删除额外的关键字，这些关键字通常由 Fwd 等邮件编辑器添加，回复:但无法提出可以满足所有这些情况的正则表达式。

Fwd : Re : Re: Many
Re : Re: Many
Re:    Re: Many
Re: Many
Re: Many
RE: Presidential Ballots for Florida
RE: (no subject)
Request - should not match anything
this is the subject
Re: Fwd

我在 Java 中尝试使用这个正则表达式:

subject.replaceAll("^.{0,3}:\s", "");

但这只会删除找到的第一个匹配项。任何正则表达式，如果它可以满足大多数常见场景，那么以上所有内容也会有很大帮助。我找到了一些适用于 Python 的正则表达式，但将它们转换为 Java 非常痛苦。感谢您的帮助。

Answer 1

您可以使用以下方法删除不仅绑定(bind)到字符串开头的事件:

\b(?:Fwd|Re)\b\h*(?::\h*)?

Regex demo

注意这也将匹配最后一行 Re: Fwd

---

如果 Fwd 不应匹配(因此冒号不是可选的)并绑定(bind)到字符串的开头:

^(?:(?:Fwd|Re)\h*:\h*)+

解释

• ^ 字符串开始
• (?: 非捕获组
  • (?:Fwd|Re)\h*:\h* 匹配 Fwd 或 Re 后跟可选水平之间的冒号空格
• )+ 关闭非捕获组，重复1+次得到所有出现

Regex demo | Java demo

例子

String regex = "^(?:(?:Fwd|Re)\\h*:\\h*)+";
String string = "Fwd : Re : Re: Many\n"
     + "Re : Re: Many\n"
     + "Re:    Re: Many\n"
     + "Re: Many\n"
     + "Re: Many\n"
     + "RE: Presidential Ballots for Florida\n"
     + "RE: (no subject)\n"
     + "Request - should not match anything\n"
     + "this is the subject\n"
     + "Re: Fwd";

Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(string);
String result = matcher.replaceAll("");

System.out.println(result);

输出

Many
Many
Many
Many
Many
Presidential Ballots for Florida
(no subject)
Request - should not match anything
this is the subject
Fwd