由Map的复制问题引发对深复制和浅复制的思考
System.out.println("user2.name:" + user2.getName());

System.out.println("user1.user.name:" + user1.getUser().getName());
System.out.println("user2.user.name:" + user2.getUser().getName());
}

public User2 getUser()
{
return user;
}

public void setUser(User2 user)
{
this.user = user;
}
}