I'm exploring the power of regular expressions, so I'm just wondering if something like this is possible:

public class StringSplit {
    public static void main(String args[]) {
        System.out.println(
            java.util.Arrays.deepToString(
                "12345".split(INSERT_REGEX_HERE)
            )
        ); // prints "[12, 23, 34, 45]"
    }
}

If possible, then simply provide the regex (and preemptively some explanation on how it works).

If it's only possible in some regex flavors other than Java, then feel free to provide those as well.

If it's not possible, then please explain why.