Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2 path $

I'm new with the retrofit library and I use version 2.4.0 I have an application where I want to show the following Json information in a ListView. Investigating I found that I expect a matrix but I receive a Json object but I have not been able to solve it for more than I have tried, does anyone have any ideas?

    [
        {
            "idalumno":"1",
            "nombre":"nombre 1",
            "direccion":"direccion 1"
        },
        {
            "idalumno":"2",
            "nombre":"nomnbre 2",
            "direccion":"direccion 2"
        },
        {
           "idalumno":"3",
           "nombre":"nombre 3",
            "direccion":"direccion 3"
        },        
    ]

When running the application I find the following error: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2 path $ and I have the following code:

public class ApiClient {

    public static final String BASE_URL = "http://192.198.1.70:8080/ws/";
    public static Retrofit retrofit = null;

    public static Retrofit getApiclient(){

        if (retrofit == null){
            retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }
        return retrofit;
    }
} 

I use the interface

public interface ApiInterface {

    @GET("obtener_alumnos.php")
    Call<List<Contact>> getContacts();
}

My object Contact

public class Contact {

    @SerializedName("name")
    private String nombre;
    private String direccion;

    public String getNombre() {
        return nombre;
    }
    public void setNombre(String nombre) {
        this.nombre = nombre;
    }
    public String getDireccion() {
        return direccion;
    }
    public void setDireccion(String direccion) {
        this.direccion = direccion;
    }
}

The OnCreate of my application

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ListView = findViewById(R.id.listView);
        apiInterface = ApiClient.getApiclient().create(ApiInterface.class);
        retrofit2.Call<List<Contact>> call = apiInterface.getContacts();

        call.enqueue(new Callback<List<Contact>>() {
            @Override
            public void onResponse(retrofit2.Call<List<Contact>> call, Response<List<Contact>> response) {

                contactList= response.body();
                adapter = new NewAdapter(getApplicationContext(),R.layout.list_item, contactList);
                ListView.setAdapter(adapter);

            }
            @Override
            public void onFailure(retrofit2.Call<List<Contact>> call, Throwable t) {
                Log.d("ERROR", t.getMessage());
                //Toast.makeText(MainActivity.this, t.getMessage(), Toast.LENGTH_LONG).show();
            }
        });
    }