Parsing CSV input with a RegEx in java

Question

I know, now I have two problems. But I\'m having fun!

I started with this advice not to try and split, but instead to match on what is an acceptable field, and expa

Answer 1

When I started to understand what I had done wrong, I also started to understand how convoluted the lookarounds were making this. I finally realized that I didn't want all the matched text, I wanted specific groups inside of it. I ended up using something very similar to my original RegEx except that I didn't do a lookahead on the closing comma, which I think should be a little more efficient. Here is my final code.

package regex.parser;

import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class CSVParser {

    /*
     * This Pattern will match on either quoted text or text between commas, including
     * whitespace, and accounting for beginning and end of line.
     */
    private final Pattern csvPattern = Pattern.compile("\"([^\"]*)\"|(?<=,|^)([^,]*)(?:,|$)");  
    private ArrayList allMatches = null;    
    private Matcher matcher = null;
    private String match = null;
    private int size;

    public CSVParser() {        
        allMatches = new ArrayList();
        matcher = null;
        match = null;
    }

    public String[] parse(String csvLine) {
        matcher = csvPattern.matcher(csvLine);
        allMatches.clear();
        String match;
        while (matcher.find()) {
            match = matcher.group(1);
            if (match!=null) {
                allMatches.add(match);
            }
            else {
                allMatches.add(matcher.group(2));
            }
        }

        size = allMatches.size();       
        if (size > 0) {
            return allMatches.toArray(new String[size]);
        }
        else {
            return new String[0];
        }           
    }   

    public static void main(String[] args) {        
        String lineinput = "the quick,\"brown, fox jumps\",over,\"the\",,\"lazy dog\"";

        CSVParser myCSV = new CSVParser();
        System.out.println("Testing CSVParser with: \n " + lineinput);
        for (String s : myCSV.parse(lineinput)) {
            System.out.println(s);
        }
    }

}