Java regular expression interpretation

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?

What kind of asking a question is that? Do you want to prevent possible helpers to cut and paste your code to test/improve it? — user unknown
– user unknown, Commented May 20, 2012 at 23:33
@Vipar StringTokenizer has actually be deprecated in favour of split. — dann.dev
– dann.dev, Commented May 20, 2012 at 23:37

Chip · Accepted Answer · 2012-05-20 23:34:58Z

5

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 : \

answered May 20, 2012 at 23:34

Chip

3,32625 silver badges31 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Terry Li Over a year ago

Why is the first backslash gone in the output?

Chip Over a year ago

@TerryLiYifeng \' means the character '. The character ' is not required to be escaped in a string but \' means '. Try it out.

Collectives™ on Stack Overflow

Java regular expression interpretation

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related