How to Encode and Decode URLs in Java

In Java, you can encode and decode URLs using the java.net.URLEncoder and java.net.URLDecoder classes. These classes handle encoding and decoding in compliance with the application/x-www-form-urlencoded MIME type.
Here’s how you can encode and decode URLs:

Code Example

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.net.URLDecoder;

public class URLEncoderDecoderExample {

    public static void main(String[] args) {
        try {
            // The String to be encoded
            String url = "https://example.com/query?name=John Doe&age=25";

            // Encoding URL
            String encodedUrl = URLEncoder.encode(url, "UTF-8");
            System.out.println("Encoded URL: " + encodedUrl);

            // Decoding URL
            String decodedUrl = URLDecoder.decode(encodedUrl, "UTF-8");
            System.out.println("Decoded URL: " + decodedUrl);

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace(); // Handle exception if unsupported encoding is provided
        }
    }
}

Explanation:

1. Encoding:
   • The URLEncoder.encode() method encodes special characters in the URL to make it safe for transmission over the network.
   • UTF-8 is typically used as the charset.
2. Decoding:
   • The URLDecoder.decode() method decodes the string back to its original format.

Sample Output:

If the input is:

https://example.com/query?name=John Doe&age=25

After encoding:

https%3A%2F%2Fexample.com%2Fquery%3Fname%3DJohn+Doe%26age%3D25

After decoding:

https://example.com/query?name=John Doe&age=25

Notes:

• Replace spaces with + in the encoded string. This is because spaces are not typically allowed in URLs, and encoding replaces them.
• Use "UTF-8" because it’s the most widely used and supports all Unicode characters.