java - Java 中类实例作为私有(private)成员

Question

我有一个作业需要使用继承和多态性:

For this assignment, we will subclass the author's Time2 class as Time3 and subclass your previous Date2 to include a Time3 instance as a private member. This new class will be called TimeStamp3 (subclassing Date2 and having a Time3 instance).

我不完全理解这部分:

include a Time3 instance as a private member

尽管我确实了解 Time3 扩展了 Time2 和 TimeStamp3 扩展了 Date2，我只是不知道需要做什么才能允许 Date2 访问 Time3。

Answer 1

创建 Time3 类后，创建另一个名为 TimeStamp3 的类(愚蠢的名称...)

public class TimeStamp3 extends Date2 {

    private Time3 time;

    //methods, other instance variables etc.

}