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This noncompliant code example takes a user input query string and build a URL. Because the URL is not properly encoded, the URL returned is not valid because it contains non-URL-safe characters RFC 1738

String buildUrl(String q) {
  //user inputs the argument "#YOLO2018"
  String url = "https://example.com?query=" + q;
 
  return url;
}

The url returned is is "https://example.com?query=#YOLO2018" which is not a valid URL.

Compliant Solution

String buildEncodedUrl(String q) {
    String origUrl = "https://example.com?query=" + q;
    String encodedUrl = Base64.getUrlEncoder().encodeToString(origUrl.getBytes());
 
    return encodedUrl;
}

The encodedUrl returned is "https%3A%2F%2Fexample.com%3Fquery%3D%23YOLO2018" which is a valid URL. Use java.util.Base64 to encode and decode when transferring binary data over mediums that only allow printable characters like URLs, filenames, and MIME.

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