public class SocialWallActivity extends AppCompatActivity{

    private Button addWall;
    private TextView mWallView;

    private DatabaseReference mDatabase;
    private TextView mUserWall;

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

        TextView social_wall = (TextView) findViewById(R.id.wall_view);

        addWall = (Button) findViewById(R.id.AddWall);
        mDatabase = FirebaseDatabase.getInstance().getReference().child(" ");
        mWallView = (TextView) findViewById(R.id.wall_view);
        mDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                String wall = dataSnapshot.getValue().toString();
                mWallView.setText("" + wall);
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

        mUserWall = (EditText) findViewById(R.id.social_wall_users_name_id);

        addWall.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                // Create Child in root object
                // assign a few values to child
                String name = mUserWall.getText().toString().trim();
                mDatabase.child("").setValue(name).addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        if(task.isSuccessful()){
                            Toast.makeText(SocialWallActivity.this, "Updated...", Toast.LENGTH_LONG).show();
                        }
                        else {
                            Toast.makeText(SocialWallActivity.this, "Error", Toast.LENGTH_LONG).show();
                        }
                    }
                });
            }
        });
    }
}