Question

I want to parse a line from a CSV(comma separated) file, something like this:

Bosh,Mark,[e-mail],"3, Institute","83, 1, 2",1,21

I have to parse the file, and instead of the commas between the apostrophes I wanna have ‘;’, like this:

Bosh,Mark,[e-mail],"3; Institute","83; 1; 2",1,21

I use the following Java code but it doesn’t parse it well:

Pattern regex = Pattern.compile("(\"[^\\]]*\")");
        Matcher matcher = regex.matcher(line);
        if (matcher.find()) {
            String replacedMatch = matcher.group();
            String gr1 = matcher.group(1);
            gr1.trim();
            replacedMatch = replacedMatch.replace(",", ";");
            line = line.replace(matcher.group(), replacedMatch);
        }

the output is:

Bosh,Mark,[e-mail],"3; Institute";"83; 1; 2",1,21

anyone have any idea how to fix this?

Answer 1

This is my solution to replace , inside quote to ;. It assumes that if " were to appear in a quoted string, then it is escaped by another ". This property ensures that counting from start to the current character, if the number of quotes " is odd, then that character is inside a quoted string.

// Test string, with the tricky case """", which resolves to
// a length 1 string of single quote "
String line = "Bosh,\"\"\"\",[e-mail],\"3, Institute\",\"83, 1, 2\",1,21";

Pattern pattern = Pattern.compile("\"[^\"]*\"");
Matcher matcher = pattern.matcher(line);

int start = 0;

StringBuilder output = new StringBuilder();

while (matcher.find()) {
  // System.out.println(m.group() + "\n " + m.start() + " " + m.end());
  output
    .append(line.substring(start, matcher.start())) // Append unrelated contents
    .append(matcher.group().replaceAll(",", ";")); // Append replaced string

  start = matcher.end();
}
output.append(line.substring(start)); // Append the rest of unrelated contents

// System.out.println(output);

Although I cannot find any case that will fail the method of replace the matched group like you did in line = line.replace(matcher.group(), replacedMatch);, I feel safer to rebuild the string from scratch.