Main entry point for accessing the Challenges data

ChallengesDataStore.java

import android.support.annotation.NonNull;

/**
* This is the main entry point for accessing the Challenges data
*/
public interface ChallengesDataStore {
    
    // Get all challenge data
    void getChallenges(@NonNull GetChallengesCallback getChallengesCallback);

    // Save all challenge data
    void saveChallenges(@NonNull Challenge challenge);

    // Clear persisted challenge data
    void deleteAllChallenges();

    // Callback interface 
    interface GetChallengesCallback {

        void onChallengesLoaded(List<Challenge> challenges);

        void onError(Exception errorMessage);

        void onDataNotAvailable();
    }
}