尝试从全局变量获取值时获取空指针异常

这是存储全局变量的类

public class GlobalVariables extends Application {
private String userToken;
private String userId;
private String userName;

public String getUserName() {
    return userName;
}

public String getUserId() {
    return userId;
}

public String getUserToken() {
    return userToken;
}

public void setUserName(String userName) {
    this.userName = userName;
}

public void setUserId(String userId) {
    this.userId = userId;
}

public void setUserToken(String userToken) {
    this.userToken = userToken;
}

}

现在我在登录类中设置值

                GlobalVariables newObj = new GlobalVariables();

                newObj.setUserId(user_values.getString("id"));

                newObj.setUserName(user_values.getString("name"));

                System.out.println(newObj.getUserId());

我在systemout中得到该值，,,但是当我尝试从另一个类中获取该值时，我得到了Null指针异常

protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.timetable);
        TextView test = (TextView) findViewById(R.id.testing);
        GlobalVariables newObj = new GlobalVariables();
        System.out.println( newObj.getUserId());


    }