Java：查找第一个Regex的索引 [英] Java: Find index of first Regex

问题描述

我需要更改一段代码包括：

I need to change a piece of code withi includes this:

string.indexOf("bc")

如果跳过bc的出现，如果前面有字母，怎么能改变这个？一个。

How can this be changed by a solutin that skips the occurence of "bc" if it is preceded by the letter "a".

我不想找到这些：

abc

但仅限：

xbc

其中x可以是除了a之外的任何东西（甚至是空的） ）。

where x can be anything but a (even empty).

我想我可以放入检查索引i-1 == a的条件，如果是，则再次调用indexOf方法。但我认为这不会产生非常漂亮的代码。

I think I could just put in a condition that checks if the index i-1 == a, and if true call the indexOf method again. But I dont think that would result in very beautiful code.

使用正则表达式的解决方案怎么样？

How would a solution that uses regular expressions look like?

编辑：看到一些回复后只是一个提示。不仅可以获得正则表达式，而且还可以获得查找索引所需的API调用。

Just a hint after seeing some responses. It would be nice to get not only the regular expression, but also the required API calls to find the index.

推荐答案

按要求一个更完整的解决方案：

As requested a more complete solution:

    /** @return index of pattern in s or -1, if not found */
public static int indexOf(Pattern pattern, String s) {
    Matcher matcher = pattern.matcher(s);
    return matcher.find() ? matcher.start() : -1;
}

致电：

int index = indexOf(Pattern.compile("(?<!a)bc"), "abc xbc");

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