Question

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Parsing CSV input with a RegEx in java

I have an input file in which each line has input values of string of the following form:

   "  ab  cd  " ,    "  efgh,ijk.",  4,"lmno"

i.e.,

1. The words are either in quotes or they have no quotes.
2. The space before and after the start and end word respectively is not allowed.

EDIT: 3. It can have inputs just separated by commas.(abc,"Hi Mary,Joe",5)

Using .Split() in java, I need a regular expression to output this:

ab  cd
efgh,ijk.
4
lmno

I tried this:

[^",]*[\",]

But this doesn’t work on "efgh,ijk."

Here is a link for regex testing: http://regexpal.com/
I need some assistance on this. Please help.
Thank you

Answer 1

DEMO

Regex pattern: (?:\s*(?:\"([^\"]*)\"|([^,]+))\s*,?)+?

Update for null values: (?:\s*(?:\"([^\"]*)\"|([^,]+))\s*,?|(?<=,)(),?)+? DEMO

An example of it working, I know it’s kinda CSV Format but as long as you dont write really really weird things it’ll match all of them.

Matcher ma = Pattern.compile("(?:\\s*(?:\\\"([^\\\"]*)\\\"|([^,]+))\\s*,?)+?").matcher("   \"  ab  cd  \" ,    \"  efgh,ijk.\",  4,\"lmno\"");
while (ma.find()) {
    if (ma.group(1) == null) {
        System.out.println(ma.group(2));
    } else {
        System.out.println(ma.group(1));
    }
}

Edit, btw if you wanted us to give the code for you, don’t tell us about a regex online tester, if you do so it’s because you know how to handle regex, if you have no idea of how to do that, ask it too.