Regular Expression to Split String based on space and matching quotes in java

Question

I have a String which i need to split based on the space and the exact matching quotes.

If the

string = \"It is fun \\\"to write\\\" regular\\\"expressi         


        

Answer 1

It seems that you just used regex from this answer, but as you could see it doesn't use split but find method from Matcher class. Also this answer takes care of ' where your input shows no signs of it.

So you can improve this regex by removing parts handling ' which will make it look like

[^\\s\"]+|\"([^\"]*)\"

Also since you want to include " as part of token then you don't need to place match from between " in separate group, so get rid of parenthesis in \"([^\"]*)\" part

[^\\s\"]+|\"[^\"]*\"

Now all you need to do is add case where there will be no closing ", but instead you will get end of string. So change this regex to

[^\\s\"]+|\"[^\"]*(\"|$)

After this you can just use Matcher, find all store tokens somewhere, lets say in List.

Example:

String data = "It is fun \"to write\" regular\"expression";
List matchList = new ArrayList();
Pattern regex = Pattern.compile("[^\\s\"]+|\"[^\"]*(\"|$)");
Matcher regexMatcher = regex.matcher(data);
while (regexMatcher.find()) {
    System.out.println(regexMatcher.group());
    matchList.add(regexMatcher.group());
}

Output:

It
is
fun
"to write"
regular
"expression

---

More complex expression to handle handle this data can look like

String data = "It is fun \"to write\" regular \"expression";
for(String s : data.split("(?

but this approach is way overcomplicated then writing your own parser.

---

Such parser could look like

public static List parse(String data) {
    List tokens = new ArrayList();
    StringBuilder sb = new StringBuilder();
    boolean insideQuote = false;
    char previous = '\0';

    for (char ch : data.toCharArray()) {
        if (ch == ' ' && !insideQuote) {
            if (sb.length() > 0 && previous != '"')
                addTokenAndResetBuilder(sb, tokens);
        } else if (ch == '"') {
            if (insideQuote) {
                sb.append(ch);
                addTokenAndResetBuilder(sb, tokens);
            } else {
                addTokenAndResetBuilder(sb, tokens);
                sb.append(ch);
            }
            insideQuote = !insideQuote;
        } else {
            sb.append(ch);
        }
        previous = ch;
    }
    addTokenAndResetBuilder(sb, tokens);

    return tokens;
}

private static void addTokenAndResetBuilder(StringBuilder sb, List list) {
    if (sb.length() > 0) {
        list.add(sb.toString());
        sb.delete(0, sb.length());
    }
}

Usage

String data = "It is fun \"to write\" regular\"expression\"xxx\"yyy";
for (String s : parse(data))
    System.out.println(s);