我的RegEx模式出了什么问题

Question

I have this pattern:

Pattern.compile(".*?\\[ISOLATION GROUP (^]+)].*");

I assumed this would match, for example, these two strings:

"[ISOLATION GROUP X] blabla"
"[OTHER FLAG][ISOLATION GROUP Y] blabla"

and then with group(1) I could get the name of the isolation group (in the above examples, "X" resp. "Y")

However the matches() is not even returning true. Why do these strings not match that pattern, what is wrong with the pattern?

Answer 1

When using a formal pattern matcher in Java, we don't need to use a pattern which matches the entire input. Instead, just use the pattern \\[ISOLATION GROUP ([^\\]]+) to get all matches:

String input = "[ISOLATION GROUP X] blabla";
input += "[OTHER FLAG][ISOLATION GROUP Y] blabla";
String pattern = "\\[ISOLATION GROUP ([^\\]]+)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(input);
while (m.find()) {
    System.out.println("Found value: " + m.group(1));
}

Found value: X
Found value: Y

Demo

Answer 2

You forgot to enclose the characters of the group within braces.

.*?\\[ISOLATION GROUP (^]+)].*

should become

.*?\\[ISOLATION GROUP ([^\\]]+)\\].*

Demo

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Positive lookbehind

Try using a positive lookbehind maybe? it is much more easier than your solution I think and you just have to deal with a single group

(?<=ISOLATION GROUP\s)[^\\]]+

Answer 3

这应该工作

Pattern.compile(".*?\\[ISOLATION GROUP .*\\].*");