shlex alternative for Java

Question

Is there a shlex alternative for Java? I'd like to be able to split quote delimited strings like the shell would process them. For example, if I'd send :

one two "three four"

and perform a split, I'd like to receive the tokens

one
two
three four

Answer 1

I had a similar problem today, and it didn't look like any standard options such as StringTokenizer, StrTokenizer, Scanner were a good fit. However, it's not hard to implement the basics.

This example handles all the edge cases currently commented on other answers. Be warned, I haven't checked it for full POSIX compliance yet. Gist including unit tests available on GitHub - released in public domain via the unlicense.

public List<String> shellSplit(CharSequence string) {
    List<String> tokens = new ArrayList<String>();
    boolean escaping = false;
    char quoteChar = ' ';
    boolean quoting = false;
    int lastCloseQuoteIndex = Integer.MIN_VALUE;
    StringBuilder current = new StringBuilder();
    for (int i = 0; i<string.length(); i++) {
        char c = string.charAt(i);
        if (escaping) {
            current.append(c);
            escaping = false;
        } else if (c == '\\' && !(quoting && quoteChar == '\'')) {
            escaping = true;
        } else if (quoting && c == quoteChar) {
            quoting = false;
            lastCloseQuoteIndex = i;
        } else if (!quoting && (c == '\'' || c == '"')) {
            quoting = true;
            quoteChar = c;
        } else if (!quoting && Character.isWhitespace(c)) {
            if (current.length() > 0 || lastCloseQuoteIndex == (i - 1)) {
                tokens.add(current.toString());
                current = new StringBuilder();
            }
        } else {
            current.append(c);
        }
    }
    if (current.length() > 0 || lastCloseQuoteIndex == (string.length() - 1)) {
        tokens.add(current.toString());
    }

    return tokens;
}