使用String的replaceAll方法删除所有标记，除非它们遵循特定的短语

Question

I have a need to replace a particular token (in this case, ? ) with another token (we can start with ! or something). String's replaceAll method will work for this. But, I don't want to replace the question mark if it happens to follow the token action . (That would be bad!)

I've tried text = text.replaceAll("[^a][^c][^t][^i][^o][^n]\\\\?","!"); but that didn't work.

For example, I want "test.action?param=lol?omg"; to turn into test.action?param=lol!omg . I know I could do something silly like

text.replaceAll("action\\?","%%%CRAZYTOKEN%%%")
    .replaceAll("\\?","!")
    .replaceAll("%%%CRAZYTOKEN%%%","action?");

but that just seems like a waste of time, especially on large strings. I'd rather do it right.

Answer 1

You need a negative look behind

text.replaceAll("(?<!action)\\?", "!");

This asserts that the ? does not follow action

Answer 2

Just use a zero-width negative lookbehind assertion to only match ? s which don't follow action :

text = text.replaceAll("(?<!action)\\?", "!");

Note the extra \\\\ before the ? . You need to escape the ? since it is a special character in regex.