Java regex split string with dashes and space

You can use

String[] result = t.split("\\s+|(?<=--)(?!-)|(?<!-)(?=--)")

See the regex demo. Details:

• \s+ - one or more whitespaces
• | - or
• (?<=--)(?!-) - a location immediately preceded with -- and not immediately followed with -
• | - or
• (?<-)(?=--) - a location not immediately preceded with - and immediately followed with --.

See the Java demo:

String regex = "\\s+|(?<=--)(?!-)|(?<!-)(?=--)";
String string = "this is my--test string";
System.out.println(Arrays.toString(string.split(regex)));
// => [this, is, my, --, test, string]

I wasn't able to do it with just regex but does this work?

String t = "this is my--test string";
t = t.replace( "--", " -- " );
String[] m = t.split(" ");

You can use a regex matcher to do this:

public static void main (String[] args) {
    final String t = "this is my--test string";
    
    final String regex = "(-+)|(\\w+)";
    final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
    final Matcher matcher = pattern.matcher(t);

    List<String> split = new ArrayList<>();
    while (matcher.find()) {
        split.add(matcher.group(0));
    }

    System.out.println(split);
}

The regex explanation:

• (-+): matches the character "-" one or multiple times;
• |: equivalent to boolean OR;
• (\\w+): matches any word character (equivalent to [a-zA-Z0-9_]) one or multiple times.

This should give you what you want and is slightly simpler than the earlier answer (which also works).

String[] m = t.split("\\s+|\\-\\-");