Project is not registering user, but does not present connection error to Database

Question

I’m doing a project on Android Studio, where a part is registering a user, I managed to make it work but after two tests of registration is presented the message of registration completed but does not appear the record in the database and also is not shown any error message in the debug of Android Studio.

Follows the code:
Class that manages the connection:

public class DB extends _Default implements Runnable {

private Connection conn;
private String host = "10.0.2.2";
private String db = "airsoft_mobile";
private int port = 5432 ;
private String user = "postgres";
private String pass = "pgadmin";


public DB() {

    super();
    this.conecta();
    this.desconecta();

}

@Override
public void run() {

    try{

        //Realiza a Conexão com o Banco de Dados
        Class.forName("org.postgresql.Driver");
        this.conn = DriverManager.getConnection("jdbc:postgresql://10.0.2.2:5432/airsoft_mobile","postgres","pgadmin");

    } catch ( Exception e ){

        this._mensagem = e.getMessage();
        this._status = false;

    }
}

public void conecta(){

    Thread thread = new Thread(this);
    thread.start();

    try{

        thread.join();

    } catch ( Exception e ){

        this._mensagem = e.getMessage();
        this._status = false;

    }

}

private void desconecta(){

    if ( this.conn != null ) {

        try {

            this.conn.close();

        }catch (Exception e){

            this._status = false;
            this._mensagem = e.getMessage();

        } finally {

            this.conn = null ;

        }

    }

}

public ResultSet select ( String query ) {

    this.conecta();
    ResultSet resultSet = null;
    try {

        resultSet = new ExecuteDB(this.conn, query).execute().get();

    } catch (Exception e) {

        this._mensagem = e.getMessage();
        this._status = false;

    }

    return resultSet;

}

public ResultSet execute ( String query ) {

    this.conecta();
    ResultSet resultSet = null;
    try {

        resultSet = new ExecuteDB(this.conn, query).execute().get();

    } catch (Exception e) {

        this._mensagem = e.getMessage();
        this._status = false;

    }

    return resultSet;

}

}

The function responsible for adding the user that is within the User class.java:

public void adicionar_usuario() {

    String comando = "";

    if ( this.getId() == -1 ) {

        comando = String.format(    "INSERT INTO usuario (nome_usuario, email_usuario, nickname_usuario, " +
                                        "senha_usuario, data_nascimento_usuario, cpf_usuario, rg_usuario, " +
                                        "tipo_usuario, telefone ) " +
                                    "VALUES ( '%s', '%s', '%s', '%s', '%s', '%s', '%s', '%s', '%s' ) " ,
                                    this.getNome(), this.getEmail(), this.getNickname(), this.getSenha(), this.getData_nasc(), this.getCpf(), this.getRg(), this.getTipo_usuario(), this.getTelefone());
    }

    DB db = new DB();
    db.execute(comando);
    this._mensagem = db._mensagem;
    this._status = db._status;

}

The function responsible for collecting data to add users:

private void adicionar(){

    String nome = txtNome.getText().toString();
    String cpf = txtCPF.getText().toString();
    String email = txtEmail.getText().toString();
    String telefone = txtTelefone.getText().toString();
    String nick = txtNick.getText().toString();
    String tipo_usuario = spnUsuario.getSelectedItem().toString();
    String senha = txtSenhaCadastro.getText().toString();
    String confirmaSenha = txtConfirmaSenha.getText().toString();

    if (! ( senha.equals(confirmaSenha) )) {

        Toast.makeText(ActCadastro.this, "As senhas não correspondem. Por favor digite novamente.", Toast.LENGTH_SHORT).show();
        txtSenhaCadastro.setText("");
        txtConfirmaSenha.setText("");

    }

    else {

        this.usuario.setNome(nome);
        this.usuario.setCpf(cpf);
        this.usuario.setEmail(email);
        this.usuario.setTelefone(telefone);
        this.usuario.setTipo_usuario(tipo_usuario);
        this.usuario.setNickname(nick);
        this.usuario.setSenha(senha);

        this.usuario.adicionar_usuario();

        Toast.makeText(ActCadastro.this, "Dados Cadastrados com Sucesso!", Toast.LENGTH_SHORT).show();


        if (tipo_usuario.equals("Sócio de Campo de Airsoft")) {

            Intent i = new Intent();
            i.setClass(ActCadastro.this, ActCadastroCampo.class);
            i.putExtra("CPF", txtCPF.getText().toString());
            startActivity(i);


        }

    }

Thanks for your help.