How to split this string in Java regex?

Question

This is the string:

String strPro = "(a0(a1)(a2 and so on)...(aN))";

Content in a son-() may be "", or just the value of strPro, or like that pattern, recursively, so a sub-() is a sub-tree.

Expected result:

str1 is "a0(a1)"
str2 is "(a2 and so on)"
...
strN is "(aN)"

str1, str2, ..., strN are e.g. elements in an Array

How to split the string?

Regex is not appropriate for parsing recursive grammars such as this. You need a real parser for this. — Jim Garrison
– Jim Garrison, Commented Apr 20, 2013 at 7:11
thanks. but even not working for just splitting strPro a time? — droidpiggy
– droidpiggy, Commented Apr 20, 2013 at 7:14

Keppil · Accepted Answer · 2013-04-20 07:14:41Z

1

You can use substring() to get rid of the outer paranthesis, and then split it using lookbehind and lookahead (?<= and ?=):

String strPro = "(a0(a1)(a2 and so on)(aN))";
String[] split = strPro.substring(1, strPro.length() - 1).split("(?<=\\))(?=\\()");
System.out.println(Arrays.toString(split));

This prints

[a0(a1), (a2 and so on), (aN)]

answered Apr 20, 2013 at 7:14

Keppil

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3 Comments

droidpiggy Over a year ago

It works well; Nice, wonderful, splendid, my English expr is poor, but thank you, Keppil

droidpiggy Over a year ago

(S(B1)(B2(B21)(B22)(B23))) --> I need only S(B1) and B2(B21)(B22)(B23)), first level, not four elements, how can I reach this?

Keppil Over a year ago

@droidpiggy: You can use split("(?<=\\))(?=\\()", 2), where the 2 is the maximum length of the result. This will only apply the splitting pattern once.

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