问题
I have a list of String that contains word. Some words have apostrophe at the beginning or/and at the end like this:
apple
'orange
banana'
joe's
I want to delete only the apostrophes at the beginning and at the end of the words like this:
apple
orange
banana
joe's
I have tried with the following regex but it doesn't work:
myString.replaceAll("((?<=^)'|'(?=$))", "");
It does not work in IntelliJ:
But it works with regex101.com:
Why the regex dosen't works and how can I remove the beginning and ending apostrophes?
Thank you for your help!
回答1:
If you plan to remove single quotes at the start or end of the line, you need to enable multiline mode (e.g. you may do it with an inline modifier (?m)):
(?m)^'|'$
As ^ and $ are anchors, zero-width assertions, you need no lookarounds to enclose these anchors with.
If you really plan to match ' that are not enclosed with word chars, use a word boundary based solution:
\B'\b|\b'\B
See the regex demo
Details:
\B'\b- a'that is preceded with a non-word boundary (there can be start of string or a non-word char immediately before') and followed with a word boundary (there must be a word char after')|- or\b'\B- a'that is preceded with a word boundary and is followed with a non-word boundary.
In Java, do not forget to use double backslashes with \b and \B:
myString = myString.replaceAll("\\B'\\b|\\b'\\B", "");
回答2:
I understand my mistake, I forgot to make the assignment…
myString = myString.replaceAll("(\B'\b)|(\b'\B)", "");
Thank you and sorry for this dumb question.
来源：https://stackoverflow.com/questions/43034731/remove-an-apostrophe-at-the-beginning-or-at-the-end-of-a-word-with-regex