private static String[] filterFromProtocols(String[] protocols,
        List<String> obsoleteProtocols) {
        if (protocols.length == 1 && obsoleteProtocols.contains(protocols[0])) {
            return EMPTY_STRING_ARRAY;
        }

        ArrayList<String> newProtocols = new ArrayList<>();
        for (String protocol : protocols) {
            if (!obsoleteProtocols.contains(protocol)) {
                newProtocols.add(protocol);
            }
        }
        return newProtocols.toArray(EMPTY_STRING_ARRAY);
    }
Returns X.509 key manager or null for none.
common/src/main/java/org/conscrypt/SSLParametersImpl.java