A DESCRIPTION OF THE REQUEST :
I suggest to add

java.net.URLEncoder.encode(String, Charset)
java.net.URLEncoder.decode(String, Charset)

methods.

JUSTIFICATION :
For a developer it's more convenient to write:

URLEncoder.encode("abc", StandardCharsets.UTF_8)

rather than:

try {
    URLEncoder.encode("abc", "utf-8");
} catch (UnsupportedEncodingException e) {
    // should never happen anyway.
}