Program: 70536
Project: 70536
Buggy source:
@Override protected void onCreate(Bundle savedInstanceState){
  super.onCreate(savedInstanceState);
  bind=DataBindingUtil.setContentView(this,R.layout.activity_chat);
  chatId=getIntent().getStringExtra(EXTRA_CHAT_ID);
  if (chatId == null)   finish();
  db=FirebaseDatabase.getInstance();
  auth=FirebaseAuth.getInstance();
  bind.send.setOnClickListener(new View.OnClickListener(){
    @Override public void onClick(    View v){
      createMessage(bind.content.getText().toString());
      bind.content.setText("String_Node_Str");
    }
  }
);
  adapter=new MessageAdapter(bind.messageList,auth.getCurrentUser().getUid());
  LinearLayoutManager linearLayoutManager=new LinearLayoutManager(this);
  linearLayoutManager.setReverseLayout(true);
  bind.messageList.setLayoutManager(linearLayoutManager);
  bind.messageList.setAdapter(adapter);
  db.getReference().child("String_Node_Str").child(chatId).child("String_Node_Str").addChildEventListener(new ChildEventListener(){
    @Override public void onChildAdded(    DataSnapshot dataSnapshot,    String s){
      db.getReference().child("String_Node_Str").child((String)dataSnapshot.getValue()).addListenerForSingleValueEvent(new ValueEventListener(){
        @Override public void onDataChange(        DataSnapshot dataSnapshot){
          adapter.addMessage(dataSnapshot.getValue(Message.class));
        }
        @Override public void onCancelled(        DatabaseError databaseError){
        }
      }
);
    }
    @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(    DatabaseError databaseError){
    }
  }
);
}

Fixed version (ground truth):
@Override protected void onCreate(Bundle savedInstanceState){
  super.onCreate(savedInstanceState);
  bind=DataBindingUtil.setContentView(this,R.layout.activity_chat);
  chatId=getIntent().getStringExtra(EXTRA_CHAT_ID);
  if (chatId == null)   finish();
  db=FirebaseDatabase.getInstance();
  auth=FirebaseAuth.getInstance();
  bind.send.setOnClickListener(new View.OnClickListener(){
    @Override public void onClick(    View v){
      createMessage(bind.content.getText().toString());
      bind.content.setText("String_Node_Str");
    }
  }
);
  adapter=new MessageAdapter(this,bind.messageList,auth.getCurrentUser().getUid());
  LinearLayoutManager linearLayoutManager=new LinearLayoutManager(this);
  linearLayoutManager.setReverseLayout(true);
  bind.messageList.setLayoutManager(linearLayoutManager);
  bind.messageList.setAdapter(adapter);
  db.getReference().child("String_Node_Str").child(chatId).child("String_Node_Str").addChildEventListener(new ChildEventListener(){
    @Override public void onChildAdded(    DataSnapshot dataSnapshot,    String s){
      db.getReference().child("String_Node_Str").child((String)dataSnapshot.getValue()).addListenerForSingleValueEvent(new ValueEventListener(){
        @Override public void onDataChange(        DataSnapshot dataSnapshot){
          adapter.addMessage(dataSnapshot.getValue(Message.class));
        }
        @Override public void onCancelled(        DatabaseError databaseError){
        }
      }
);
    }
    @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(    DatabaseError databaseError){
    }
  }
);
}