remove query parameter with java string operations

Question

I have a simple problem and yet to find the optimal solution.

Imagine I have a url with a query param named 'id' like any of the following formats

• xxxxxxxxxxxxx?id=123
• xxxxxxxxxxxxx?id=123&xxxxxxxx
• xxxxxxxxxxxxx?xxxxxx&id=123
• xxxxxxxxxxxxx?xxxxxx&id=123&xxxxx

I'm taking the above string (could be any one above) as a String parameter and want to figure out the simplest way to remove the query parameter id (name and value), so that even after removing, it will be a valid url.

Below are my expected outputs (in order).

• xxxxxxxxxxxxx
• xxxxxxxxxxxxx?xxxxxxxx
• xxxxxxxxxxxxx?xxxxxx
• xxxxxxxxxxxxx?xxxxxx&xxxxx

Can anyone have a good idea? (only with String operations, without any util classes)

Answer 1

You can use replaceAll which is using regex like so :

String[] urls = new String[]{
    "xxxxxxxxxxxxx?id=123", "xxxxxxxxxxxxx?id=123&xxxxxxxx", 
    "xxxxxxxxxxxxx?xxxxxx&id=123", "xxxxxxxxxxxxx?xxxxxx&id=123&xxxxx"
};
for (String url : urls) {
    System.out.println(
            url.replaceAll("([\\?&]id=\\d+$)|(id=\\d+&)", "")
    );
}

Output

xxxxxxxxxxxxx
xxxxxxxxxxxxx?xxxxxxxx
xxxxxxxxxxxxx?xxxxxx
xxxxxxxxxxxxx?xxxxxx&xxxxx

---

Demo

Regex demo

---

Details

this regex ([\?&]id=\d+$)|(id=\d+&) mean to match :

• ([\?&]id=\d+$) first group
  • [\?&] match literal ? or & character
  • id followed by literal id word
  • \d+ followed by one or mode digit
  • $ end of line
• | or
• (id=\d+&) match group two
  • id match literal id word
  • \d+ followed by one or mode digit
  • & match literal & character

If you the input after id= can be other than a digit you can use \w instead which match \w word character which can match any character in [A-Za-z0-9_]

Answer 2

Another approach without regex:

String removeParameter(String url, String paramToRemove) {
    String[] parts = url.split("\\?");
    if (parts.length == 2) {
        String base = parts[0];
        String params = parts[1];

        return base + "?" + Stream.of(params.split("&"))
                .map(p -> p.split("="))
                .filter(p -> !p[0].equals(paramToRemove))
                .map(p -> String.join("=", p))
                .collect(Collectors.joining("&"));
    } else {
        return url;
    }
}

And use it like this:

removeParameter("xxxxxxxxxxxxx?xxxxxx&id=123", "id") // xxxxxxxxxxxxx?xxxxxx