@Nullable
    @Override
    public Boolean defaultPreferHttp1() {
        final Boolean defaultPreferHttp1 = getBoolean("defaultPreferHttp1");
        if (defaultPreferHttp1 != null) {
            return defaultPreferHttp1;
        }
        return getBoolean("preferHttp1");
    }
Implementation of {@link FlagsProvider} which provides values from JVM options to {@link Flags}.
core/src/main/java/com/linecorp/armeria/common/SystemPropertyFlagsProvider.java