java - Unlimited quantifiers in a complex lookbehind -

java - Unlimited quantifiers in a complex lookbehind -

i'm having lot of problem writing regular expression:

(?<=\s+|^\s*|\(\s*|\.)(?:item|item1|item2)(?=\s+|\s*$|\s*\)|\.)

it works on regex editor (expresso) , in .net environment, in java environment (jre 1.6.0.25 using eclipse helios r2) doesn't work because pattern.compile() method throws "syntax error u_regex_look_behind_limit" exception.

that's because behind pattern (?<=\s+|^\s*|\(\s*|\.) must have defined limit (unlimited quantifiers such * , + not allowed here far know).

i tried specify range of repetition in way no luck:

(?<=\s{0,1000}|^\s{0,1000}|\(\s{0,1000}|\.)(?:item|item1|item2)(?=\s+|\s*$|\s*\)|\.)

so, how can write identical regex works on java environment? can't believe there's no workaround kind of mutual situation....

keep in mind lookbehind far behind must. example, (?<=\s+) satisfied if previous character space; doesn't need farther back.

the same true of lookbehind. if it's not origin of string , previous character not whitespace, open-parenthesis or period, there's no point looking farther back. it's equivalent this:

(?<=^|[\s(.])

your lookahead can condensed in same way. if it's not end of string, , next character not whitespace, close-parenthesis or period, there's no point looking further:

(?=[\s).]|$)

so final regex is:

(?<=^|[\s(.])(?:item|item1|item2)(?=[\s).]|$)

java regex lookbehind