Structuring the data with objects

Create a model class with constructors and declare a string to fetch the database reference for a unique key to add the list of objects. The model class is as follows: 

public class Users {

    private String Name;
    private String Email;
    private String Phone;

    public Users() {
    }

    public String getName() {
        return Name;
    }

    public void setName(String name) {
        Name = name;
    }

    public String getEmail() {
        return Email;
    }

    public void setEmail(String email) {
        Email = email;
    }

    public String getPhone() {
        return Phone;
    }

    public void setPhone(String phone) {
        Phone = phone;
    }

    public Users(String name, String email, String phone) {
        Name = name;
        Email = email;
        Phone = phone;
    }

}

Now in the activity class using the DatabaseReference class we can set the object value to Firebase, as follows:

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private FirebaseDatabase mDatabase;
    private DatabaseReference mDbRef;
    private String userId;

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

        // Write a message to the database
        mDatabase = FirebaseDatabase.getInstance();
        mDbRef = mDatabase.getReference("Donor/Name");

        //Setting firebase unique key for Hashmap list
        String userId = mDbRef.push().getKey();
        // creating user object
        Users user = new Users("Hillary", "hillary@xyz.com", "90097863873", "Tokyo");

        mDbRef.child(userId).setValue(user);

    }
}

The preceding code will add the object into Firebase as follows: