How to Create Chat Application using Firebase in Android

public class MessageSource {
private static final Firebase sRef = new Firebase("YOUR APP URL");
private static SimpleDateFormat sDateFormat = new SimpleDateFormat("yyyyMMddmmss");
private static final String TAG = "MessageDataSource";
private static final String COLUMN_TEXT = "text";
private static final String COLUMN_SENDER = "sender";

public static void saveMessage(Message message, String convoId){
Date date = message.getmDate();
String key = sDateFormat.format(date);
HashMap<String, String> msg = new HashMap<>();
msg.put(COLUMN_TEXT, message.getmText());
msg.put(COLUMN_SENDER,"Barun");
sRef.child(convoId).child(key).setValue(msg);
}

public static MessagesListener addMessagesListener(String convoId, final MessagesCallbacks callbacks){
MessagesListener listener = new MessagesListener(callbacks);
sRef.child(convoId).addChildEventListener(listener);
return listener;
}

public static void stop(MessagesListener listener){
sRef.removeEventListener(listener);
}

public static class MessagesListener implements ChildEventListener {
private MessagesCallbacks callbacks;
MessagesListener(MessagesCallbacks callbacks){
this.callbacks = callbacks;
}

@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
HashMap<String,String> msg = (HashMap)dataSnapshot.getValue();
Message message = new Message();
message.setmSender(msg.get(COLUMN_SENDER));
message.setmText(msg.get(COLUMN_TEXT)); 
try {
message.setmDate(sDateFormat.parse(dataSnapshot.getKey()));
}catch (Exception e){
Log.d(TAG, "Couldn't parse date"+e);
}
if(callbacks != null){
callbacks.onMessageAdded(message);
}
}

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

@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
}

public interface MessagesCallbacks{
public void onMessageAdded(Message message);
}
}

7.Create a new Class  named  Message.java and add the following code inside it