public class MainActivity extends AppCompatActivity {
EditText userName;
EditText password;
Button signInbtn;
DatabaseReference url;
Map<String, User> users = new HashMap<String, User>();
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final FirebaseDatabase database = FirebaseDatabase.getInstance();
    url = database.getInstance().getReference();
    userName = (EditText) findViewById(R.id.userName);
    loader = (ProgressBar) findViewById(R.id.loader);
    password = (EditText) findViewById(R.id.password);
    signInbtn = (Button) findViewById(R.id.signInBtn);
    signInbtn.setOnClickListener(signObject);

}  View.OnClickListener signObject = new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        User user = new User("Moshe","1234");
        users.put("101",user);
        DatabaseReference userUrl = url.child("Users");
        userUrl.setValue(users);
        System.out.println(users);
    }
};

public static String password;
public static String name ;

public User(){

}

public User(String name,String password){
    this.name = name;
    this.password = password;
}

public  String getName() {
    return name;
}

public  void setName(String name) {
    User.name = name;
}

public  String getPassword() {
    return password;
}

public  void setPassword(String password) {
    User.password = password;
}