Question

import java.util.regex.*;

public class Splitter {
    public static void main(String[] args) throws Exception {
        Pattern p = Pattern.compile("[,\\s]+");
        String[] results = p.split("one,two, three   four ,  five");
        for (String result : results) {
            System.out.println(result);
        }
    }
}

The splitter is either a comma or a whitespace or a combination of any number of them. I thought the regular expression for it should be [,\s]+. Why was there an extra backslash in the example?

Answer 1

The extra \ is to escape the next backslash. In any Java string "\\" means "\".

This is because the '\' is a special character. You must have seen "\n" used to mean newline right? So to put a literal \ in a string you use "\\".

For example try System.out.println("Here\'s a backslash : \\").

This will print :
Here's a backslash : \