How to split string with round brackets in it?

Question

Got a String:

String s = "1+2*(30+4/2-(1+2))*2+1";

Got method to split a string:

    public void convertString(String s) {
        String[] arr = s.split("(?<=[\\d.])(?=[^\\d.])|(?<=[^\\d.])(?=[\\d.])");
}

problem is:

    Output:
    [1, +, 2, *(, 30, +, 4, /, 2, -(, 1, +, 2, ))*, 2, +, 1] 
    //here round brackets store in the same cell with next symbol or prev symbol   *(,  ))*,

expected output:

[1, +, 2, *, (, 30, +, 4, /, 2, -, (, 1, +, 2, ), ), *, 2, +, 1]
// here round brackets store in a separate arr cells

I need to store round brackets in the separate array cells.

How to achieve it?

if not using regexps, digit values may contains with errors, for example 30 may be store like 3, 0 — Dartweiler, Nov 09 '20 at 14:27
I mean that using regular expressions might be a not very good idea for you (especially for recursive parenthesis), and what you might need is implementing a lexer whose classic problem is parsing math expressions like the one you've provided. — terrorrussia-keeps-killing, Nov 09 '20 at 14:32
[This](https://stackoverflow.com/a/47570657/1707353) looks like a reasonable implementation. You might be able to substitute `+*/-` with `+*/-()`. — Jeff Holt, Nov 09 '20 at 14:35

score 3 · Accepted Answer · answered Nov 09 '20 at 14:32

Your regex literally splits at any location that goes from non-digit to digit, or vice versa. It explicitly does not split between non-digits.

So give your current method, the fix would be

public void convertString(String s) {
    String[] arr = s.split("(?<=[\\d.])(?=[^\\d.])|(?<=[^\\d.])(?=[^\\d.])|(?<=[^\\d.])(?=[\\d.])");
}

That said, it's probably better ways of doing this. A simple regex match, where the expression is either a single-non-digit, or an eager group of digits, will already be easier than this.

score 0 · Answer 2 · answered Nov 09 '20 at 14:39

0

don't include brackets in your regex, only take out the specific punctuation which you don't want. you can create an array and use a loop to put the numbers into the array. https://regex101.com/r/tHjoYn/1/ - here you can test for the regex you want.

answered Nov 09 '20 at 14:39

Gil Caplan

64
8

How to split string with round brackets in it?

2 Answers2