• The same URL can be encoded multiple times, we need to decode it until the URL cannnot be decoded further. For example, “video%252Fmp4” is the result of two encodings. Upon decoding it once, we get “video%2Fmp4”. Now the URL needs to be further decoded so that we get “video/mp4”, which is the result.
• We use the decode method of a predefined Java class named URLDecoder.
• The decode method of URLDecoder takes two arguments:
  • The first argument defines the URL to be decoded.
  • The second argument defines the decoding scheme to be used.
• After decoding, the resulting decoded URL is returned.
• We create two variables: prevURL, which is empty, and decodeURL, which contains the URL to be decoded.
• We create an iteration that runs until prevURL!=decodeURL
• Now we update prevURL to decodeURL and update decodeURL with the decoded value of the URL passed.
• As you can see, prevURL!=decodeURL, so we run it again and again.
• Now, prevURL=decodeURL, so the decoded URL is returned.

Sample Code

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
 
public class DecodeURLExample {
    public static void main(String a[]){
        try {
            System.out.println(URLDecoder.decode("special+chars%3A+%26%25*+", "UTF-8"));
        } catch (UnsupportedEncodingException ex) {
            ex.printStackTrace();
        }
    }
}

special chars: &%*