Arrays.asList returns a fixed-size List backed by the array. If you want a normal mutable java.util.ArrayList you need to do this:

List<String> list = new ArrayList<String>(Arrays.asList(string.split(" , ")));

Or, using Guava:

List<String> list = Lists.newArrayList(Splitter.on(" , ").split(string));

Using a Splitter gives you more flexibility in how you split the string and gives you the ability to, for example, skip empty strings in the results and trim results. It also has less weird behavior than String.split as well as not requiring you to split by regex (that's just one option).

You can do a regular expression.

@Test
public void test() {
    List<String> delimiters = Arrays.asList(",", ".", "?");
    String str = "a.b,c?dr";

    StringBuilder regex = new StringBuilder();
    regex.append("[");
    delimiters.stream().forEach(delimiter -> regex.append(delimiter + "/"));
    regex.append("]");

    String[] result = str.split(regex.toString());
}

I still suggest to use split(), it skips null tokens by default. you want to get rid of non numeric characters in the string and only keep pipes and numbers, then you can easily use split() to get what you want. or you can pass multiple delimiters to split (in form of regex) and this should work:

String[] splited = yourString.split("[\\|\\s]+");

and the regex:

import java.util.regex.*;

Pattern pattern = Pattern.compile("\\d+(?=([\\|\\s\\r\\n]))");
Matcher matcher = pattern.matcher(yourString);
while (matcher.find()) {
    System.out.println(matcher.group());
}