how to make and AsyncCallback deliver data before next method is called - for-loop

Question

I have a method that calls 2 services that make AsyncCallBacks
centroService.buscarCentroPorNombre(nombreCentroSeleccionado, new AsyncCallback<Centro>() {
#Override
public void onSuccess(Centro centro) {
cArticuloCentro.setIdCentro(centro.getIdCentro());
cArticuloCentro.setPrecio(Double.parseDouble(precioTextBox.getText()));
}
#Override
public void onFailure(Throwable caught) {
//do something
}
});
articuloService.buscarArticuloPorNombre(nombreArticuloSeleccionado, new AsyncCallback<Articulo>() { //se llama al sevivio para q busque el la base de datos la Entity por nombre
public void onSuccess(Articulo articulo) {
cArticuloCentro.setIdArticulo(articulo.getCod());
}
#Override
public void onFailure(Throwable caught) {
//do something
}
});
the problem comes when the next method is called
becouse these serviceCalls are asynchronous method activates before the calls are made, does not getting desired data. next method is
save(){
articuloCentroService.saveArticuloCentro(cArticuloCentro, new AsyncCallback<String>() {
#Override
public void onFailure(Throwable caught) {
//do something
}
#Override
public void onSuccess(String result) {
Window.alert("saved");
}
});
}
please can you tell me a way to make save() method execute when the asyncCallbacks have finished
thank you

Answer 1

In pure java you would need to synchronize threads, but in GWT, there's only one thread running at all times, so you can do a simply sync logic using an array:
final int[] sync = new int[1];
centroService.buscarCentroPorNombre(nombreCentroSeleccionado, new AsyncCallback<Centro>() {
#Override
public void onSuccess(Centro centro){
//...
if (++sync[0] == 2){
save();
}
}
#Override
public void onFailure(Throwable caught) {
//do something
}
});
articuloService.buscarArticuloPorNombre(nombreArticuloSeleccionado, new AsyncCallback<Articulo>() {
public void onSuccess(Articulo articulo) {
//...
if (++sync[0] == 2){
save();
}
}
#Override
public void onFailure(Throwable caught) {
//do something
}
});
Explanation: since there's only one thread running, the sync array will only be updated by one thread at a time. You can't control which method will finish first, but when they do, only one callback will be executed at a time. The sync array is just a counter you can use to sync any number of async invocations.