Why does String.replaceAll() work differently in Java 8 from Java 9?












28















Why does this code output 02 in java-8 but o2 in java-9 or above?



"o2".replaceAll("([oO])([^[0-9-]])", "0$2")





java regex string java-8 java-9







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  • 7





    A simplification of the code that still shows the behaviour : Pattern.matches("[^[x]]", "x") returns true with JDK8 and false with JDK9+.

    – Aaron
    9 hours ago


















28















Why does this code output 02 in java-8 but o2 in java-9 or above?



"o2".replaceAll("([oO])([^[0-9-]])", "0$2")





java regex string java-8 java-9







share|improve this question




















  • 7





    A simplification of the code that still shows the behaviour : Pattern.matches("[^[x]]", "x") returns true with JDK8 and false with JDK9+.

    – Aaron
    9 hours ago
















28












28








28


7






Why does this code output 02 in java-8 but o2 in java-9 or above?



"o2".replaceAll("([oO])([^[0-9-]])", "0$2")





java regex string java-8 java-9







share|improve this question
















Why does this code output 02 in java-8 but o2 in java-9 or above?



"o2".replaceAll("([oO])([^[0-9-]])", "0$2")





java regex string java-8 java-9




java regex string java-8 java-9






share|improve this question















share|improve this question













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share|improve this question








edited 8 hours ago









Boann

37.1k1290121




37.1k1290121










asked 9 hours ago









Fuyang LiuFuyang Liu

592417




592417








  • 7





    A simplification of the code that still shows the behaviour : Pattern.matches("[^[x]]", "x") returns true with JDK8 and false with JDK9+.

    – Aaron
    9 hours ago
















  • 7





    A simplification of the code that still shows the behaviour : Pattern.matches("[^[x]]", "x") returns true with JDK8 and false with JDK9+.

    – Aaron
    9 hours ago










7




7





A simplification of the code that still shows the behaviour : Pattern.matches("[^[x]]", "x") returns true with JDK8 and false with JDK9+.

– Aaron
9 hours ago







A simplification of the code that still shows the behaviour : Pattern.matches("[^[x]]", "x") returns true with JDK8 and false with JDK9+.

– Aaron
9 hours ago














1 Answer
1






active

oldest

votes


















35














Most likely due to JDK-6609854 and JDK-8189343 which reported negative nested character classes handling (in your example [^[0-9-]]). This behavior was fixed in 9 and 10, but fix was not backported to 8. The bug for Java 8 is explained as:




In Java, the negation does not apply to anything appearing in
nested [brackets]



So [^c] does not match "c", as you would expect.



[^[c]] does match "c". Not what I would expect.



[[^c]] does not match "c"



The same holds true for ranges or property expressions - if they're
inside brackets, a negation at an out level does not affect them.



[^a-z] is opposite from [^[a-z]]







share|improve this answer





















  • 6





    You can't prove the regex does not match the string at regex101, it does not support character class union. In PCRE, [^[0-9-]] matches a char that is not [, digit and - and then a ].

    – Wiktor Stribiżew
    9 hours ago








  • 1





    @WiktorStribiżew removed, thanks. Would you suggest some other online tool that supports them?

    – Karol Dowbecki
    9 hours ago








  • 3





    Use RegexPlanet

    – Wiktor Stribiżew
    9 hours ago






  • 9





    In case it's not obvious -- the OP can fix this inconsistency by changing [^[0-9-]] to [^0-9-].

    – ruakh
    9 hours ago











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1 Answer
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1 Answer
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active

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35














Most likely due to JDK-6609854 and JDK-8189343 which reported negative nested character classes handling (in your example [^[0-9-]]). This behavior was fixed in 9 and 10, but fix was not backported to 8. The bug for Java 8 is explained as:




In Java, the negation does not apply to anything appearing in
nested [brackets]



So [^c] does not match "c", as you would expect.



[^[c]] does match "c". Not what I would expect.



[[^c]] does not match "c"



The same holds true for ranges or property expressions - if they're
inside brackets, a negation at an out level does not affect them.



[^a-z] is opposite from [^[a-z]]







share|improve this answer





















  • 6





    You can't prove the regex does not match the string at regex101, it does not support character class union. In PCRE, [^[0-9-]] matches a char that is not [, digit and - and then a ].

    – Wiktor Stribiżew
    9 hours ago








  • 1





    @WiktorStribiżew removed, thanks. Would you suggest some other online tool that supports them?

    – Karol Dowbecki
    9 hours ago








  • 3





    Use RegexPlanet

    – Wiktor Stribiżew
    9 hours ago






  • 9





    In case it's not obvious -- the OP can fix this inconsistency by changing [^[0-9-]] to [^0-9-].

    – ruakh
    9 hours ago
















35














Most likely due to JDK-6609854 and JDK-8189343 which reported negative nested character classes handling (in your example [^[0-9-]]). This behavior was fixed in 9 and 10, but fix was not backported to 8. The bug for Java 8 is explained as:




In Java, the negation does not apply to anything appearing in
nested [brackets]



So [^c] does not match "c", as you would expect.



[^[c]] does match "c". Not what I would expect.



[[^c]] does not match "c"



The same holds true for ranges or property expressions - if they're
inside brackets, a negation at an out level does not affect them.



[^a-z] is opposite from [^[a-z]]







share|improve this answer





















  • 6





    You can't prove the regex does not match the string at regex101, it does not support character class union. In PCRE, [^[0-9-]] matches a char that is not [, digit and - and then a ].

    – Wiktor Stribiżew
    9 hours ago








  • 1





    @WiktorStribiżew removed, thanks. Would you suggest some other online tool that supports them?

    – Karol Dowbecki
    9 hours ago








  • 3





    Use RegexPlanet

    – Wiktor Stribiżew
    9 hours ago






  • 9





    In case it's not obvious -- the OP can fix this inconsistency by changing [^[0-9-]] to [^0-9-].

    – ruakh
    9 hours ago














35












35








35







Most likely due to JDK-6609854 and JDK-8189343 which reported negative nested character classes handling (in your example [^[0-9-]]). This behavior was fixed in 9 and 10, but fix was not backported to 8. The bug for Java 8 is explained as:




In Java, the negation does not apply to anything appearing in
nested [brackets]



So [^c] does not match "c", as you would expect.



[^[c]] does match "c". Not what I would expect.



[[^c]] does not match "c"



The same holds true for ranges or property expressions - if they're
inside brackets, a negation at an out level does not affect them.



[^a-z] is opposite from [^[a-z]]







share|improve this answer















Most likely due to JDK-6609854 and JDK-8189343 which reported negative nested character classes handling (in your example [^[0-9-]]). This behavior was fixed in 9 and 10, but fix was not backported to 8. The bug for Java 8 is explained as:




In Java, the negation does not apply to anything appearing in
nested [brackets]



So [^c] does not match "c", as you would expect.



[^[c]] does match "c". Not what I would expect.



[[^c]] does not match "c"



The same holds true for ranges or property expressions - if they're
inside brackets, a negation at an out level does not affect them.



[^a-z] is opposite from [^[a-z]]








share|improve this answer














share|improve this answer



share|improve this answer








edited 5 hours ago

























answered 9 hours ago









Karol DowbeckiKarol Dowbecki

22.6k93455




22.6k93455








  • 6





    You can't prove the regex does not match the string at regex101, it does not support character class union. In PCRE, [^[0-9-]] matches a char that is not [, digit and - and then a ].

    – Wiktor Stribiżew
    9 hours ago








  • 1





    @WiktorStribiżew removed, thanks. Would you suggest some other online tool that supports them?

    – Karol Dowbecki
    9 hours ago








  • 3





    Use RegexPlanet

    – Wiktor Stribiżew
    9 hours ago






  • 9





    In case it's not obvious -- the OP can fix this inconsistency by changing [^[0-9-]] to [^0-9-].

    – ruakh
    9 hours ago














  • 6





    You can't prove the regex does not match the string at regex101, it does not support character class union. In PCRE, [^[0-9-]] matches a char that is not [, digit and - and then a ].

    – Wiktor Stribiżew
    9 hours ago








  • 1





    @WiktorStribiżew removed, thanks. Would you suggest some other online tool that supports them?

    – Karol Dowbecki
    9 hours ago








  • 3





    Use RegexPlanet

    – Wiktor Stribiżew
    9 hours ago






  • 9





    In case it's not obvious -- the OP can fix this inconsistency by changing [^[0-9-]] to [^0-9-].

    – ruakh
    9 hours ago








6




6





You can't prove the regex does not match the string at regex101, it does not support character class union. In PCRE, [^[0-9-]] matches a char that is not [, digit and - and then a ].

– Wiktor Stribiżew
9 hours ago







You can't prove the regex does not match the string at regex101, it does not support character class union. In PCRE, [^[0-9-]] matches a char that is not [, digit and - and then a ].

– Wiktor Stribiżew
9 hours ago






1




1





@WiktorStribiżew removed, thanks. Would you suggest some other online tool that supports them?

– Karol Dowbecki
9 hours ago







@WiktorStribiżew removed, thanks. Would you suggest some other online tool that supports them?

– Karol Dowbecki
9 hours ago






3




3





Use RegexPlanet

– Wiktor Stribiżew
9 hours ago





Use RegexPlanet

– Wiktor Stribiżew
9 hours ago




9




9





In case it's not obvious -- the OP can fix this inconsistency by changing [^[0-9-]] to [^0-9-].

– ruakh
9 hours ago





In case it's not obvious -- the OP can fix this inconsistency by changing [^[0-9-]] to [^0-9-].

– ruakh
9 hours ago




















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