问题描述
我找到了来提取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])
按预期工作：
- value - > value
- camelValue - > camel / Value
- TitleValue - > Title / Value
例如使用Java：
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+低字符）
- 如果n个字符在最后，该组应该是：（n个字符）。
关于如何改进这个的任何想法正则表达式？
Any idea on how to improve this regex?
推荐答案
以下正则表达式适用于以上所有示例：
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);
}
}
它的作用是强迫负面的观察不仅忽略匹配字符串的开头，但也要忽略大写字母前面有另一个大写字母的匹配项。这会处理像VALUE这样的情况。
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] 。此子句允许在每个大写字母之前进行拆分后跟一个小写字母，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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