private boolean canEncodeToISO8859_1(final String input) {
        if (iso8859_1Encoder == null) {
            iso8859_1Encoder = StandardCharsets.ISO_8859_1.newEncoder();
        }
        return iso8859_1Encoder.canEncode(input);
    }
Determines whether the given string can be encoded in ISO-8859-1 without loss of data.
This is used to decide whether the {@code filename} parameter can be used as-is or if
the {@code filename*} parameter is needed for non-ISO-8859-1 characters.

@param input the string to check, must not be {@code null}
@return {@code true} if the string can be encoded in ISO-8859-1, {@code false} otherwise
@since 5.5
httpclient5/src/main/java/org/apache/hc/client5/http/entity/mime/FormBodyPartBuilder.java