include::../description.adoc[]

include::../ask-yourself.adoc[]

include::../recommended.adoc[]

== Sensitive Code Example

The first regex evaluation will never end in ``++JDK++`` +<=+ 9 and the second regex evaluation will never end in any versions of the ``++JDK++``:

----
java.util.regex.Pattern.compile("(a+)+").matcher(
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"+
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"+
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"+
"aaaaaaaaaaaaaaa!").matches(); // Sensitive

java.util.regex.Pattern.compile("(h|h|ih(((i|a|c|c|a|i|i|j|b|a|i|b|a|a|j))+h)ahbfhba|c|i)*").matcher(
"hchcchicihcchciiicichhcichcihcchiihichiciiiihhcchi"+
"cchhcihchcihiihciichhccciccichcichiihcchcihhicchcciicchcccihiiihhihihihi"+
"chicihhcciccchihhhcchichchciihiicihciihcccciciccicciiiiiiiiicihhhiiiihchccch"+
"chhhhiiihchihcccchhhiiiiiiiicicichicihcciciihichhhhchihciiihhiccccccciciihh"+
"ichiccchhicchicihihccichicciihcichccihhiciccccccccichhhhihihhcchchihih"+
"iihhihihihicichihiiiihhhhihhhchhichiicihhiiiiihchccccchichci").matches(); // Sensitive
----

== Compliant Solution

Possessive quantifiers do not keep backtracking positions, thus can be used, if possible, to avoid performance issues:

----
java.util.regex.Pattern.compile("(a+)++").matcher(
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"+
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"+
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"+
"aaaaaaaaaaaaaaa!").matches(); // Compliant

java.util.regex.Pattern.compile("(h|h|ih(((i|a|c|c|a|i|i|j|b|a|i|b|a|a|j))+h)ahbfhba|c|i)*+").matcher(
"hchcchicihcchciiicichhcichcihcchiihichiciiiihhcchi"+
"cchhcihchcihiihciichhccciccichcichiihcchcihhicchcciicchcccihiiihhihihihi"+
"chicihhcciccchihhhcchichchciihiicihciihcccciciccicciiiiiiiiicihhhiiiihchccch"+
"chhhhiiihchihcccchhhiiiiiiiicicichicihcciciihichhhhchihciiihhiccccccciciihh"+
"ichiccchhicchicihihccichicciihcichccihhiciccccccccichhhhihihhcchchihih"+
"iihhihihihicichihiiiihhhhihhhchhichiicihhiiiiihchccccchichci").matches(); // Compliant
----

include::../see.adoc[]

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

include::../message.adoc[]

'''
== Comments And Links
(visible only on this page)

include::../comments-and-links.adoc[]
endif::env-github,rspecator-view[]