public class Test1{

  public static void main(String[] args){

    User u = new User();

    u.no = 40;

    u.name = "ajflasd ";

    u.address = new address();

    //name、no都是引用，它们存储的是堆内存中对应实例变量的地址

  }

}

public class D34_husband_and_wife{

  public static void main(String[] args){  

    Husband huangxiaoming = new Husband();

    Wife baby = new Wife();

    huangxiaoming.name = "huangxiaoming";

    baby.name = "baby";

    //上面的例子其实将两个人割裂开来，没有建立关系

    //下面对她们进行建立关系

    huangxiaoming.w = baby;

    baby.h = huangxiaoming;  

​


  }

}

class Wife {

  String name;

  Husband h;

}

class Husband {

  String name;

  Wife w;

}