{"id":30320,"date":"2023-01-14T13:30:43","date_gmt":"2023-01-14T08:00:43","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-a-regex-that-doesnt-match-with-this-character-sequence\/"},"modified":"2023-01-14T13:30:43","modified_gmt":"2023-01-14T08:00:43","slug":"solved-a-regex-that-doesnt-match-with-this-character-sequence","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-a-regex-that-doesnt-match-with-this-character-sequence\/","title":{"rendered":"[Solved] A regex that doesn’t match with this character sequence"},"content":{"rendered":"

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This answer is to demonstrate the possibility only. Using it in production code is questionable.<\/strong><\/p>\n

It is possible with Java String replaceAll<\/code> function:<\/p>\n

String input = \"Hi, Mr.Xyz! Your account number is :- (1234567890) , (.*) &$@%#*(....))(((\";\nString output = input.replaceAll(\"\\\\G((?:[^()\\\\[\\\\]{}?+\\\\\\\\.$^*|!&@#%_\\\":<>\/;'`~-]|\\\\Q(.*)\\\\E)*+)([()\\\\[\\\\]{}?+\\\\\\\\.$^*|!&@#%_\\\":<>\/;'`~-])\", \"$1\\\\\\\\$2\");\n<\/code><\/pre>\n
Result:<\/p>\n
\"Hi, Mr\\.Xyz\\! Your account number is \\:\\- \\(1234567890\\) , (.*) \\&\\$\\@\\%\\#\\*\\(\\.\\.\\.\\.\\)\\)\\(\\(\\(\"\n<\/code><\/pre>\n
Another test:<\/p>\n
String input = \"(.*) sdfHi test message <> >>>>><<<<f<f<,,,,<> <>(.*) sdf (.*)  sdf (.*)\";\n<\/code><\/pre>\n
Result:<\/p>\n
\"(.*) sdfHi test message \\<\\> \\>\\>\\>\\>\\>\\<\\<\\<\\<f\\<f\\<,,,,\\<\\> \\<\\>(.*) sdf (.*)  sdf (.*)\"\n<\/code><\/pre>\n
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Explanation<\/strong><\/p>\n
Raw regex:<\/p>\n
\\G((?:[^()\\[\\]{}?+\\\\.$^*|!&@#%_\":<>\/;'`~-]|\\Q(.*)\\E)*+)([()\\[\\]{}?+\\\\.$^*|!&@#%_\":<>\/;'`~-])\n<\/code><\/pre>\n
Note that \\<\/code> is escaped once more when the regex is specified inside the string, and \"<\/code> needs to be escaped. The resulting regex in string can be seen above.<\/p>\n
Raw replacement string:<\/p>\n
$1\\\\$2\n<\/code><\/pre>\n
Since $<\/code> has special meaning in replacement string, and you want to keep<\/strong> it for $2<\/code>, you need to escape the \\<\/code> so that \\<\/code> won’t escape the $<\/code>. And putting the replacement string in quoted string, you need to double up the number of \\<\/code> to escape the \\<\/code>.<\/p>\n
Before we dissect the monster, let’s talk about the idea. We will consume non-special characters, and the sequence that we don’t want to replace, and as many times as possible. The next character will either be a special character not forming sequence we don’t want to replace, or is the end of the string (which means that we have found all character that needs replacing if any).<\/p>\n
Naturally, we can think of any arbitrary string as consisting of many of the following pattern consecutively: [0 or more (non-special character or special pattern not to be replace)][special character]<\/code>, and the string ends with [0 or more (non-special character or special pattern not to be replace)]<\/code>.<\/p>\n
replaceAll<\/code> function when used with a regex without \\G<\/code> may find matches that are not consecutive, which can cut in the middle of the sequence not to be replaced and mess it up. \\G<\/code> means the boundary of last match, and can be used to make sure the next match starts from where the last match left off.<\/p>\n