正则表达式拆分驼峰式或标题式(高级) [英] RegEx to split camelCase or TitleCase (advanced)

问题描述

我找到了一个 出色的 RegEx 来提取camelCase 或 TitleCase 表达式的一部分.

I found a brilliant RegEx to extract the part of a camelCase or TitleCase expression.

 (?<!^)(?=[A-Z])

它按预期工作:

• 价值 -> 价值
• camelValue -> 骆驼/值
• TitleValue -> 标题/价值

以 Java 为例:

String s = "loremIpsum";
words = s.split("(?<!^)(?=[A-Z])");
//words equals words = new String[]{"lorem","Ipsum"}

我的问题是它在某些情况下不起作用:

My problem is that it does not work in some cases:

• 案例 1:VALUE -> V/A/L/U/E
• 案例 2:eclipseRCPExt -> eclipse/R/C/P/Ext

在我看来，结果应该是:

To my mind, the result shoud be:

• 案例 1:VALUE
• 案例 2:eclipse/RCP/Ext

换句话说，给定 n 个大写字符:

In other words, given n uppercase chars:

• 如果 n 个字符后跟小写字符，则组应为:(n-1 个字符)/(第 n 个字符 + 小写字符)
• 如果 n 个字符在末尾，则该组应为:(n 个字符).

知道如何改进这个正则表达式吗?

Any idea on how to improve this regex?

推荐答案

以下正则表达式适用于上述所有示例:

The following regex works for all of the above examples:

public static void main(String[] args)
{
    for (String w : "camelValue".split("(?<!(^|[A-Z]))(?=[A-Z])|(?<!^)(?=[A-Z][a-z])")) {
        System.out.println(w);
    }
}   

它的工作原理是强制否定后视不仅忽​​略字符串开头的匹配项，而且还忽略大写字母前面是另一个大写字母的匹配项.这可以处理诸如VALUE"之类的情况.

It works by forcing the negative lookbehind to not only ignore matches at the start of the string, but to also ignore matches where a capital letter is preceded by another capital letter. This handles cases like "VALUE".

由于未能在RPC"和Ext"之间拆分，正则表达式的第一部分本身在eclipseRCPExt"上失败.这是第二个子句的目的:(?<!^)(?=[AZ][az].这个子句允许在每个大写字母前跟一个小写字母前进行拆分，除了在字符串的开头.

The first part of the regex on its own fails on "eclipseRCPExt" by failing to split between "RPC" and "Ext". This is the purpose of the second clause: (?<!^)(?=[A-Z][a-z]. This clause allows a split before every capital letter that is followed by a lowercase letter, except at the start of the string.

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