NullPointerException Trying to do a Preferences Activity

Question

Hi i am trying to make a preferences Activity that keeps all the information about a card game and return it. The information arrives from a spinner item selection. The problem arrives when I create a Objet of my class "Configuracion" and I call the method to open SharedPreferences I receive a NullPointerException. What is my problem? thank you!

public class Configuracion extends ActionBarActivity {
private String array_spinner [];


private int numerojugadores;
private int numerobarajas;
private int numerocartas;
private String nombrejugador;

private String numerojug_s = "";



SharedPreferences sp;
SharedPreferences sp1;

private Spinner s;


@Override
public void onBackPressed() {
    finish();
    return;
}  

public void EstablecerConfiguracion(){


        // Here's when fails when I create a "Configuracion" Object from other class 
        // and I call that method
        sp1= getSharedPreferences ("config", Context.MODE_PRIVATE);

        sp1.getString("NUM_JUG", numerojug_s);
        //          sp.getString("NUM_BAR", "1");
        //          sp.getString("NUM_CAR", "3");
        //          sp.getString("NOM_JUG", "Jugador_Sardi");



        switch (sp1.getString("NUM_JUG", numerojug_s)){

        case "2":this.numerojugadores = 2;break;
        case "3":this.numerojugadores = 3;break;
        case "4":this.numerojugadores = 4;break;
        case "5":this.numerojugadores = 5;break;
        default: this.numerojugadores = 2;System.out.println("ALGO PASA MAL");break;
        }
        System.out.println(numerojug_s);





}


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);







    setContentView(R.layout.activity_configuracion);
    array_spinner=new String[4];
    array_spinner[0]="2";
    array_spinner[1]="3";
    array_spinner[2]="4";
    array_spinner[3]="5";
    s = (Spinner) findViewById(R.id.spinner1);
    //        s.setSelection(2);
    ArrayAdapter adapter = new ArrayAdapter(this,
    android.R.layout.simple_spinner_item, array_spinner);
    s.setAdapter(adapter);



    s.setOnItemSelectedListener(listener_numjug);  



}

protected void onResume(){

    super.onResume();


    sp = getSharedPreferences("config",Context.MODE_PRIVATE);

    sp.getString("NUM_JUG", numerojug_s);
    sp.getString("NUM_BAR", "1");
    sp.getString("NUM_CAR", "3");
    sp.getString("NOM_JUG", "Jugador_Sardi");



    switch (sp.getString("NUM_JUG", numerojug_s)){

    case "2": s.setSelection(0);break;
    case "3": s.setSelection(1);break;
    case "4": s.setSelection(2);break;
    case "5": s.setSelection(3);break;
    default: s.setSelection(0);System.out.println("ALGO PASA MAL");break;
    }
    System.out.println(numerojug_s);


}



OnItemSelectedListener listener_numjug = new OnItemSelectedListener() {

    @Override
    public void onItemSelected(AdapterView<?> parent, View view,
            int position, long id) {
        // TODO Auto-generated method stub
        System.out.println(position + " POSICION");


        Editor edit = sp.edit();

        switch(position){

        case 0: edit.putString("NUM_JUG", "2"); edit.commit();numerojug_s = "2";break;
        case 1: edit.putString("NUM_JUG", "3"); edit.commit();numerojug_s = "3";break;
        case 2: edit.putString("NUM_JUG", "4"); edit.commit();numerojug_s = "4";break;
        case 3: edit.putString("NUM_JUG", "5"); edit.commit();numerojug_s = "5";break;


        }

    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        // TODO Auto-generated method stub

    }};  


public int getNumJug(){

   //       sp = getSharedPreferences("config",Context.MODE_PRIVATE);

    sp.getString("NUM_JUG", numerojug_s);


    return this.numerojugadores;
}

public int getNumBar(){
    return this.numerobarajas;
}

public int getNumCar(){
    return this.numerocartas;
}
public String getNomJug(){
    return this.nombrejugador;
}


public  void setNumJug(int numeroJug){
    this.numerojugadores = numeroJug;
}

public void setNumBar(int numeroBar){
    this.numerobarajas = numeroBar;
}

public void setNumCar(int numeroCar){
    this.numerocartas = numeroCar;
}
public void getNomJug(String nombreJug){
     this.nombrejugador = nombreJug;
}

}