When creating an ILcdModel for a single WMS layer, you can skip the creation of a TLcdWMSDataSource by specifying the needed layer directly in the server URL: 

String serverURL = "https://sampleservices.luciad.com/wms";
String wmsLayerName = "cities";

//Concat the url and layer name to a single string
String sourceName = String.format("%s?data=%s", serverURL, wmsLayerName);

//Decode the model
ILcdModelDecoder decoder = new TLcdOGCWMSProxyModelDecoder();
ILcdModel model = decoder.decode(sourceName);

is the equivalent of

String serverURL = "https://sampleservices.luciad.com/wms";
String wmsLayerName = "cities";

//Create the data source
TLcdWMSDataSource dataSource = TLcdWMSDataSource.newBuilder()
                                                .uri(serverURL)
                                                .addLayer(wmsLayerName)
                                                .build();

//Decode the model
ILcdModelDecoder decoder = new TLcdOGCWMSProxyModelDecoder();
ILcdModel model = decoder.decodeSource(dataSource);