java将字符串（Cookie）保存到SharedPrefs导致NullPointerException

Question

我用创建了一个类来帮助我处理身份验证（将Cookie保存到SharedPrefs）

public class Authentication extends Application {

    String PREFS_NAME = "UserData";
    String DEFAULT = "";

    Context context;
    public static SharedPreferences sharedPreferences;
    public static SharedPreferences.Editor editor;
    public static String token;

    public Authentication(Activity context) {
        this.context = context;
        sharedPreferences = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
        editor = sharedPreferences.edit();
        token = sharedPreferences.getString("Cookie", DEFAULT);
    }

    //speichert Token in den Shared Preferences
    public static void setToken(String token) {
        Log.d("Cookie", token);
        editor.putString("Cookie", token);
        }
}

当我调用Authentication.setToken(token)-方法作为我的响应（RegisterActivity）时，我会得到一个NullPointerException：

java.lang.NullPointerException: Attempt to invoke interface method '安卓.content.SharedPreferences$Editor 安卓.content.SharedPreferences$Editor.putString(java.lang.String, java.lang.String)' on a null object reference

你们谁能帮我解决这个问题吗？提前谢谢