Command parsing with quotes within quotes

Question

I have been trying to parse a command with regular expression in Java for a while but no success. The main issue I am having is that the delimiter is space and then I want to treat everything that is within a double quotes as an argument but what if one of these arg contains quotes within quotes. Here is the command and few examples:

my_command "regex or text" <"regex or text"|NA> <"text or regex"|NA> integer integer 

Example1: my_command "Simple case" NA NA 2 3 

Example2: my_command "This is it!" "[\",;']" "Really?" 3 5

Example3: my_command "Not so fast" NA "Another regex int the mix [\"a-zA-Z123]" 1 1

Basically parseCommand(String str) will take any of the above examples and return a List with the following values:

Example1: list[0] = "Simple Case", list[1] = NA, list[2] = NA, list[3] = "2", list[4] = "3"

Example2: list[0] = "This is it!", list[1] = "[\",;']", list[2] = NA, list[3] = "3", list[4] = "5"
Example3: list[0] = "Not so fast", list[1] = NA, list[2] = "Another regex int the mix [\"a-zA-Z123]" , list[3] = "1", list[4] = "1"

Thank you for your help in advance.

Answer 1

Trying to do this with a regex is a mistake - you are not parsing a regular expression .

Start with something like this - you will fail with a regex:

public void test() {
    System.out.println(parse("\"This is it!\" \"[\\\",;']\" \"Really?\" 3 5"));
}

List<String> parse(String s) {
    List<String> parsed = new ArrayList<String>();
    boolean inQuotes = false;
    boolean escape = false;
    int from = 0;
    for (int i = 0; i < s.length(); i++) {
        char ch = s.charAt(i);
        switch (ch) {
            case ' ':
                if (!inQuotes && !escape) {
                    parsed.add(s.substring(from, i));
                    from = i + 1;
                }
                break;
            case '\"':
                if (!escape) {
                    inQuotes = !inQuotes;
                }
                escape = false;
                break;
            case '\\':
                escape = !escape;
                break;
            default:
                escape = false;
                break;
        }
    }

    if (from < s.length()) {
        parsed.add(s.substring(from, s.length()));
    }
    return parsed;
}

Added

With the specific string in question, here is my interpretation:

String str = "my_command \"Something [\"abc']\" \"text\" NA 1 1";
//                         ............        ..       .......
//                        ^            ^      ^  ^     ^

I have used a ^ to indicate a quote and used . for all characters therefore in quotes. Thus no further splits after the first quote as there are no unquoted spaces after that.