使用正则表达式获取第三个正斜杠（“ /”）之后的字符

Question

I've been trying to get the substring, after the third forward slash (" / ") from a string.

http://www.google.com/search?q=Regular+Expressions while stopping before ? and # if they are present in the string.

I have the regex:

Pattern regex = Pattern.compile(":\\/\\/[0-9a-zA-Z-\\.:]+(\\/)([^?#]*)$");

however it doesn't work with every string

I also came up with the regex:

Pattern regex = Pattern.compile("(.*)?:\\/\\/[^#?]*);

however this one grabs everything before the third forward slash (" / ").

What am I doing wrong? Thanks

Answer 1

You could try

(?:.*?\/){3}([^\/?#]+)

or in java

(?:.*?\\/){3}([^\\/?#]+)

(escaped backslashes).

It matches anything up to, and including, a slash - three times. Then captures everything up to, not including, a slash, question mark or hash sign.

Result is in capture group 1.

Check it out here at regex101 .

Answer 2

This regex will work in java :

    public static void main(String[] args) throws Exception {
    String s = "http://www.google.com/search?q=Regular+Expressions";
    String regex = "(?:.*?/){2}.*?(/\\w+)(\\?|#).*"; // Don't capture anything upto the 3rd "/" then capture everything until you get a "?" or a "#" and then don't capture the rest. Replace everything with the captured value
    String str = s.replaceAll(regex, "$1");
    System.out.println(str);
    String s2 = "https://www.google.com/hello?test#";
    String str2 = s2.replaceAll(regex, "$1");
    System.out.println(str2);

}

O/P :

/search
/hello