public EurekaEndpointGroupBuilder vipAddress(String vipAddress) {
        requireNonNull(vipAddress, "vipAddress");
        checkArgument(!vipAddress.isEmpty(), "vipAddress is empty.");
        checkState(appName == null && instanceId == null && secureVipAddress == null,
                   "cannot set vipAddress with the %s.",
                   secureVipAddress != null ? "secureVipAddress" : "appName or instanceId");
        this.vipAddress = vipAddress;
        return this;
    }
Sets the specified {@code vipAddress}. {@link EurekaEndpointGroup} will retrieve the registry information
whose VIP address is the specified {@code vipAddress}.

@throws IllegalStateException if {@link #appName(String)}, {@link #instanceId(String)} or
                              {@link #secureVipAddress(String)} is called already
eureka/src/main/java/com/linecorp/armeria/client/eureka/EurekaEndpointGroupBuilder.java