How to retrieve more than one key-value from the firebase using customAdapter

i am having problem in retrieving more than one key by using customAdapter.

Can you share your code?

Main Activity.java
package com.example.eleventure.virtualwaiter;

import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

import com.google.firebase.FirebaseApp;
import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity
{

ArrayList <Order> newOrder = new ArrayList<>();
ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    listView= findViewById(R.id.listView);

    final CustomAdapter customAdapter = new CustomAdapter();
    listView.setAdapter(customAdapter);



    //Retrieving Data from Firebase Starts from here
    FirebaseApp.initializeApp(MainActivity.this);
    final DatabaseReference dbRef = FirebaseDatabase.getInstance().getReference();

    dbRef.child("coffee-time-a17ac").addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
            Order data = dataSnapshot.getValue(Order.class);
            newOrder.add(data);
            customAdapter.notifyDataSetChanged();
        }

        @Override
        public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {

        }

        @Override
        public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {

        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });
}


//And ends here


//Custom  Array  Adapter Starts Here


class CustomAdapter extends BaseAdapter{

    @Override
    public int getCount() {
        return newOrder.size();
    }

    @Override
    public Order getItem(int position) {
        return newOrder.get(position);
    }

    @Override
    public long getItemId(int i) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View itemView=getLayoutInflater().inflate(
                R.layout.order_item,
                parent,
                false
        );

        TextView Coffee_type=itemView.findViewById(R.id.Coffee_type);
        TextView size = itemView.findViewById(R.id.size);
        TextView number = itemView.findViewById(R.id.number);

        Coffee_type.setText(getItem(position).getCoffee_types());
        size.setText(getItem(position).getSize());
        number.setText(getItem(position).getNumber());

        return itemView;
    }
}
//Custom Array Adapter Ends Here

}

Order.java
package com.example.eleventure.virtualwaiter;

public class Order {

String Coffee_types;
String size;
String number;

public Order() {
}

public Order(String coffee_types, String size, String number) {
    Coffee_types = coffee_types;
    this.size = size;
    this.number = number;
}

public String getCoffee_types() {
    return Coffee_types;
}

public String getSize() {
    return size;
}

public String getNumber() {
    return number;
}

}

The code that you have shared seems correct to me.

Screenshot%20(76)

This is my data in database which i am trying to retrieve.
I had made several changes in code like in Order.java - I have changed the name from Coffee_types to coffeeTypes as per naming convention and adjusted the constructors and getters according to it,but it is still showing errors

Could you connect with me on TeamViewer?