Step by Step solution about How to resolve the algorithm URL encoding step by step in the Java programming language

Java Code to Encode Strings for URL Addresses

Goal: The code provides a method (encode) for encoding strings to adhere to URL address requirements.

Specific Encoding Rules:

• Characters that remain unchanged: -, ., _, ~, *
• Space characters are replaced with '+'
• Alphanumeric characters (A-Z, a-z, 0-9) are kept as is
• All other characters are escaped using their UTF-8 hexadecimal value, preceded by %

Implementation Details:

• encode(String string) method:

  • Iterates over the characters of the input string
  • Checks each character against specified rules
  • Modifies the character accordingly (either kept, replaced, or escaped)
  • Builds an encoded string and returns it

• alphanumeric(char character) method:

  • Checks if a character is alphanumeric (letters or digits)
  • Returns true if it is, false otherwise

Usage:

The code includes an example of encoding a string using the encode method:

URLEncoder.encode("http://foo bar/", StandardCharsets.UTF_8)

This will encode the string "http://foo bar/" according to the rules mentioned above, resulting in "http%3A%2F%2Ffoo+bar%2F".

Additional Notes:

• The code uses UTF-8 encoding as specified by the StandardCharsets.UTF_8 constant.
• The encode method can be used to encode any string, not just URLs.
• This encoding method is commonly used in web applications and other scenarios where strings need to be transmitted in a URL-safe format.

import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;


URLEncoder.encode("http://foo bar/", StandardCharsets.UTF_8)


String encode(String string) {
    StringBuilder encoded = new StringBuilder();
    for (char character : string.toCharArray()) {
        switch (character) {
            /* rfc3986 and html5 */
            case '-', '.', '_', '~', '*' -> encoded.append(character);
            case ' ' -> encoded.append('+');
            default -> {
                if (alphanumeric(character))
                    encoded.append(character);
                else {
                    encoded.append("%");
                    encoded.append("%02x".formatted((int) character));
                }
            }
        }
    }
    return encoded.toString();
}

boolean alphanumeric(char character) {
    return (character >= 'A' && character <= 'Z')
        || (character >= 'a' && character <= 'z')
        || (character >= '0' && character <= '9');
}