String.split() *not* on regular expression?

Since String.split() works with regular expressions, this snippet:

String s = "str?str?argh";
s.split("r?");

... yields: [, s, t, , ?, s, t, , ?, a, , g, h]

What's the most elegant way to split this String on the r? sequence so that it produces [st, st, argh]?

EDIT: I know that I can escape the problematic ?. The trouble is I don't know the delimiter offhand and I don't feel like working this around by writing an escapeGenericRegex() function.

A general solution using just Java SE APIs is:

String separator = ...
s.split(Pattern.quote(separator));

The quote method returns a regex that will match the argument string as a literal.

You can use

StringUtils.split("?r")

from commons-lang.

This works perfect as well:

public static List<String> splitNonRegex(String input, String delim)
{
    List<String> l = new ArrayList<String>();
    int offset = 0;

    while (true)
    {
        int index = input.indexOf(delim, offset);
        if (index == -1)
        {
            l.add(input.substring(offset));
            return l;
        } else
        {
            l.add(input.substring(offset, index));
            offset = (index + delim.length());
        }
    }
}

Escape the ?:

s.split("r\\?");

Use Guava Splitter:

>Extracts non-overlapping substrings from an input string, typically by recognizing appearances of a separator sequence. This separator can be specified as a single character, fixed string, regular expression or CharMatcher instance. Or, instead of using a separator at all, a splitter can extract adjacent substrings of a given fixed length.

String[] strs = str.split(Pattern.quote("r?"));

Using directly the Pattern class, is possible to define the expression as LITERAL, and in that case, the expression will be evaluated as is (not regex expression).

Pattern.compile(<literalExpression>, Pattern.LITERAL).split(<stringToBeSplitted>);

example:

String[] result = Pattern.compile("r?", Pattern.LITERAL).split("str?str?argh");

will result:

[st, st, argh]

org.apache.commons.lang.StringUtils has methods for splitting Strings without expensive regular expressions.

Be sure to read the javadocs closely as the behavior can be subtle. StringUtils.split (as in another answer) does not meet the stated requirements. Use StringUtils.splitByWholeSeparator instead:

String s = "str?str?argh";

StringUtils.split(s, "r?");                   //[st, st, a, gh]
StringUtils.splitByWholeSeparator(s, "r?");   //[st, st, argh]

try

String s = "str?str?argh";
s.split("r\?");