Почему checkBox не isChecked

Подскажите почему когда я закрываю приложение и снова открываю то у меня checkBox не становятся isChecked.

public  class Adapter_class2 extends RecyclerView.Adapter<Adapter_class2.ViewHolder> {
private LayoutInflater inflater1;
private List<ModelClass2> modelClass2;
boolean checked=true;
Context context;
Adapter_class2(Context context, List<ModelClass2> modelClass) {
    this.modelClass2 = modelClass;
    this.inflater1 = LayoutInflater.from(context);
    this.context=context;
}
@Override
public Adapter_class2.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = inflater1.inflate(R.layout.item_layout2, parent, false);
    return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull Adapter_class2.ViewHolder viewHolder, int i) {
    ModelClass2 model_class = modelClass2.get(i);
    viewHolder.imageView_ex.setImageResource(model_class.getImage_resourse());
  viewHolder.kol_times.setText(model_class.getText_for_times());
  viewHolder.name_exercise.setText(model_class.getText_for_ex());
  switch (i){
      case 0: viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox1", false));break;
      case 1:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox2", false));break;
      case 2:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox3", false));break;
      case 3:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox4", false));break;
      case 4:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox6", false));break;
      case 5:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox6", false));break;
      case 6:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox7", false));break;
      case 7:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox8", false));break;
      case 8:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox9", false));break;
      case 9:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox10", false));break;
      case 10:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox11", false));break;
      case 11:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox12", false));break;
      case 12:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox13", false));break;
      case 13:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox14", false));break;
      case 14:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox15", false));break;
      case 15:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox16", false));break;
      case 16:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox17", false));break;
      case 17:viewHolder.checkBox.setChecked(PreferenceManager.getDefaultSharedPreferences(context)
              .getBoolean("checkBox18", false));break;
  }
  if(viewHolder.checkBox.isChecked()){
      switch (i){
          case 0:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox1", checked).commit();break;//для первого checkBox
          case 1:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox2", checked).commit();break;//для второго checkBox
          case 2:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox3", checked).commit();;//для третьего checkBox
          case 3:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox4", checked).commit();break;//для четвертого checkBox
          case 4:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox5", checked).commit();break;//для пятго  checkBox
          case 5:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox6", checked).commit();break;//для шестого checkBox
          case 6:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox7", checked).commit();break;//и т.д
          case 7:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox8", checked).commit();break;
          case 8:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox9", checked).commit();break;
          case 9:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox10", checked).commit();break;
          case 10:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox11", checked).commit();break;
          case 11:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox12", checked).commit();break;
          case 12:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox13", checked).commit();break;
          case 13:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox14", checked).commit();break;
          case 14:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox15", checked).commit();break;
          case 15:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox16", checked).commit();break;
          case 16:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox17", checked).commit();break;
          case 17:PreferenceManager.getDefaultSharedPreferences(context).edit()
                  .putBoolean("checkBox18", checked).commit();break;

      }
  }
}

@Override
public int getItemCount() {
    return modelClass2.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
    final TextView name_exercise;
    final TextView kol_times;
    final ImageView imageView_ex;
    final CheckBox checkBox;
    ViewHolder(View view) {
        super(view);
        name_exercise=view.findViewById(R.id.textView11);
        kol_times=view.findViewById(R.id.textView12);
        imageView_ex=view.findViewById(R.id.imageView5);
        checkBox =view.findViewById(R.id.checkBox5);
        boolean checked = PreferenceManager.getDefaultSharedPreferences(context)
                .getBoolean("checkBox1", false);
    }
}

}