GatewayServer.java

public class GatewayServer extends Server {

    private double ratio;
    private PaymentGateway gateway;

    public GatewayServer(String host, int port, double ratio, PaymentGateway gateway) {
        super(host, port);
        this.ratio = ratio;
        this.gateway = gateway;
    }

    public double getRatio() {
        return ratio;
    }

    public void setRatio(double ratio) {
        this.ratio = ratio;
    }

    public PaymentGateway getGateway() {
        return gateway;
    }
}