You need

test.split("\\|");

split uses regular expression and in regex | is a metacharacter representing the OR operator. You need to escape that character using \ (written in String as "\\" since \ is also a metacharacter in String literals and require another \ to escape it).

You can also use

test.split(Pattern.quote("|"));

and let Pattern.quote create the escaped version of the regex representing |.

String.split takes a regular expression as argument.

This means you can alternate whatever symbol or text abstraction in one parameter in order to split your String.

See documentation here.

Here's an example in your case:

String toSplit = "a+b-c*d/e=f";
String[] splitted = toSplit.split("[-+*/=]");
for (String split: splitted) {
    System.out.println(split);
}

Output:

a
b
c
d
e
f

Notes:

• Reserved characters for Patterns must be double-escaped with \\. Edit: Not needed here.
• The [] brackets in the pattern indicate a character class.
• More on Patterns here.

You should use a non word i.e \W

\W is inverse of \w

\W is similar to [^a-zA-Z0-9_] and so would match any non-word character except _

OR

you can simply use [^a-zA-Z0-9]