import java.util.*;
import java.util.regex.*;

class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String regex = "\\s+|(?<=--)(?!--)|(?<!--)(?=--)";
        String string = "this is my--test string";
		System.out.println(Arrays.toString(string.split(regex)));

	}
}