How to strip down a string to the first duplicate?

Question

I have converted a few web pages into string and the string contains these lines(along with other code):

<div class="r"><a href="https://www.apple.com/ca/"
<div class="r"><a href="https://www.facebook.com/ca/"
<div class="r"><a href="https://www.utorrent.com/ca/"

but I just want to strip out the link inside the first line(https://www.apple.com/ca/) and ignore the rest of the HTML and the code. How do I do that?

Bohemian · Accepted Answer · 2020-09-19T00:58:18.657

2

The easy way:

String url = input.replaceAll("(?s).*?href=\"(.*?)\".*", "$1");

Key points of why this works:

regex matches the whole input, but captures the target. The replacement is the capture (group #1). This approach effectively extracts the target
(?s) means “dot matches newline”
.*? is reluctantly (as little input as possible) matches up to “href"”
(.*?) capture (reluctantly) everything up to “"”
.* greedily (as much as possible) matches the rest (thanks to (?s) above)
replacement is $1 - the first (and only) group in the match

edited Sep 19 '20 at 00:58

answered Sep 19 '20 at 00:37

Bohemian

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Excuse my brevity but how did you do that?? – Dr cola Sep 19 '20 at 00:50
@Drcola see edited answer for explanation – Bohemian Sep 19 '20 at 00:58

score 1 · Answer 2 · answered Sep 18 '20 at 22:49

Using the regex mentioned in the answer, given below is the solution using the Java regex API:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {
    public static void main(String[] args) {
        String str = "<div class=\"r\"><a href=\"https://www.apple.com/ca/\">Hello</a>\n"
                + "<div class=\"r\"><a href=\"https://www.facebook.com/ca/\">Hello</a>\n"
                + "<div class=\"r\"><a href=\"https://www.utorrent.com/ca/\">Hello</a>";
        String regex = "\\b(https?|ftp|file)://[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(str);
        while (matcher.find()) {
            System.out.println(matcher.group());
        }
    }
}

Output:

https://www.apple.com/ca/
https://www.facebook.com/ca/
https://www.utorrent.com/ca/

Hey sir, this is no good because the code is set up to look for the first visible url in the string. The problem is, I want the first URL after the line ` — Dr cola, Sep 18 '20 at 23:34
This doesn’t actually answer the question, which was to get *the first* URL *only*. You could add a `break` to the loop, but it sure is a lot of code. — Bohemian, Sep 19 '20 at 01:03

How to strip down a string to the first duplicate?

2 Answers2