Repository to retreive the database elements

app/src/main/java/fr/romanet/vj/apps/myweather/repository/CityRepository.java

@@ -0,0 +1,56 @@
+package fr.romanet.vj.apps.myweather.repository;
+
+import android.content.Context;
+import androidx.room.Room;
+import java.util.List;
+import fr.romanet.vj.apps.myweather.bo.City;
+import fr.romanet.vj.apps.myweather.database.CityDatabase;
+
+public final class CityRepository
+{
+    private static volatile CityRepository instance;
+
+    // We accept the "out-of-order writes" case
+    public static CityRepository getInstance(Context context)
+    {
+        if (instance == null)
+        {
+            synchronized (CityRepository.class)
+            {
+                if (instance == null)
+                {
+                    instance = new CityRepository(context);
+                }
+            }
+        }
+        return instance;
+    }
+
+    private final CityDatabase cityDatabase;
+
+    private CityRepository(Context context)
+    {
+        cityDatabase = Room.databaseBuilder(context, CityDatabase.class, "city-database").allowMainThreadQueries().build();
+    }
+
+    public List<City> getCity()
+    {
+        return cityDatabase.cityDao().getCity();
+    }
+
+    public void deleteCity(City cityToDelete)
+    {
+        cityDatabase.cityDao().deleteCity(cityToDelete);
+    }
+
+    public void addCity(City cityToAdd)
+    {
+        cityDatabase.cityDao().addCity(cityToAdd);
+    }
+
+    public List<City> sortCityByName()
+    {
+        return cityDatabase.cityDao().sortCityByName();
+    }
+
+}