static String requireNonNullAllCapsNonEmpty(String input) {
        if (input == null) {
            throw new IllegalArgumentException("Null argument not allowed.");
        }
        if (!input.trim().equals(input)) {
            throw new IllegalArgumentException("Leading or trailing whitespace is not allowed.");
        }
        if (input.isEmpty()) {
            throw new IllegalArgumentException("Empty string is not allowed.");
        }
        if (!input.toUpperCase(Locale.ROOT).equals(input)) {
            throw new IllegalArgumentException("String must be UPPERCASE.");
        }
        return input;
    }
An endpoint for a raft quorum voter.
clients/src/main/java/org/apache/kafka/clients/admin/RaftVoterEndpoint.java