Splitting a Java String by the pipe symbol using split("|")

The Java official documentation states:

The string "boo:and:foo", for example, yields the following results with these expressions Regex Result :

{ "boo", "and", "foo" }"

And that's the way I need it to work. However, if I run this:

public static void main(String[] args){
        String test = "A|B|C||D";

        String[] result = test.split("|");

        for(String s : result){
            System.out.println(">"+s+"<");
        }
    }

it prints:

><
>A<
>|<
>B<
>|<
>C<
>|<
>|<
>D<

Which is far from what I would expect:

>A<
>B<
>C<
><
>D<

Why is this happening?

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 |.

Use proper escaping: string.split("\\|")

Or, in Java 5+, use the helper Pattern.quote() which has been created for exactly this purpose:

string.split(Pattern.quote("|"))

which works with arbitrary input strings. Very useful when you need to quote / escape user input.