@Override
    public String toString() {
        return new StringJoiner(", ", JavaSysPropsProxySettings.class.getSimpleName() + "[", "]")
            .add("nonProxyHosts=" + nonProxyHosts)
            .add("proxy=" + proxy)
            .add("noProxyRegex=" + noProxyRegex)
            .toString();
    }
Whether a proxy has been defined given the parameters it was constructed with.

For example, if the provided system properties keys resolve null, then this will return {@code false}.

@return true, if a proxy has been defined, otherwise false.
gateway/platforms/vertx3/vertx3/src/main/java/io/apiman/gateway/platforms/vertx3/engine/proxy/JavaSysPropsProxySettings.java