Splitting on comma outside quotes

Why Split when you can Match?

Resurrecting this question because for some reason, the easy solution wasn't mentioned. Here is our beautifully compact regex:

"[^"]*"|[^,]+

This will match all the desired fragments (see demo).

Explanation

• With "[^"]*", we match complete "double-quoted strings"
• or |
• we match [^,]+ any characters that are not a comma.

A possible refinement is to improve the string side of the alternation to allow the quoted strings to include escaped quotes.

You can try out this regex:

str.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)");

This splits the string on , that is followed by an even number of double quotes. In other words, it splits on comma outside the double quotes. This will work provided you have balanced quotes in your string.

Explanation:

,           // Split on comma
(?=         // Followed by
   (?:      // Start a non-capture group
     [^"]*  // 0 or more non-quote characters
     "      // 1 quote
     [^"]*  // 0 or more non-quote characters
     "      // 1 quote
   )*       // 0 or more repetition of non-capture group (multiple of 2 quotes will be even)
   [^"]*    // Finally 0 or more non-quotes
   $        // Till the end  (This is necessary, else every comma will satisfy the condition)
)

You can even type like this in your code, using (?x) modifier with your regex. The modifier ignores any whitespaces in your regex, so it's becomes more easy to read a regex broken into multiple lines like so:

String[] arr = str.split("(?x)   " + 
                     ",          " +   // Split on comma
                     "(?=        " +   // Followed by
                     "  (?:      " +   // Start a non-capture group
                     "    [^\"]* " +   // 0 or more non-quote characters
                     "    \"     " +   // 1 quote
                     "    [^\"]* " +   // 0 or more non-quote characters
                     "    \"     " +   // 1 quote
                     "  )*       " +   // 0 or more repetition of non-capture group (multiple of 2 quotes will be even)
                     "  [^\"]*   " +   // Finally 0 or more non-quotes
                     "  $        " +   // Till the end  (This is necessary, else every comma will satisfy the condition)
                     ")          "     // End look-ahead
                         );