Hi Sergiu, Could you have a look at BoldTest.testTimeComplexity(). It generates a stackoverflow error in the console: java.lang.StackOverflowError at java.util.regex.ASCII.isType(ASCII.java:185) at java.util.regex.Pattern$Ctype.isSatisfiedBy(Pattern.java:3444) at java.util.regex.Pattern$CharProperty$1.isSatisfiedBy(Pattern.java: 3337) at java.util.regex.Pattern$CharProperty.match(Pattern.java:3345) at java.util.regex.Pattern$GroupHead.match(Pattern.java:4168) at java.util.regex.Pattern$Behind.match(Pattern.java:4648) at java.util.regex.Pattern$LazyLoop.match(Pattern.java:4353) at java.util.regex.Pattern$GroupTail.match(Pattern.java:4227) at java.util.regex.Pattern$BranchConn.match(Pattern.java:4078) at java.util.regex.Pattern$Curly.match2(Pattern.java:3821) at java.util.regex.Pattern$Curly.match(Pattern.java:3748) at java.util.regex.Pattern$Branch.match(Pattern.java:4114) at java.util.regex.Pattern$GroupHead.match(Pattern.java:4168) Thanks -Vincent