跨类传递数据

public class User {
    private String id;
    private String username;
    private String gender;
    // ...
}

public class UserStorage {
    public static ThreadLocal<User> USER = new ThreadLocal();
    
    public static void setUser(User user) {
        USER.set(user);
    }
}

// A类设置值
public class classA {
    public static void main(String[] args) {
        User user = new User("1", "zhangsan", "man");
        
        UserStorage.setUser(user);
    }
}

// B类获取值
public class classB {
    public static void main(String[] args) {    
        User user = UserStorage.USER.get();
    }
}