当我阅读JDK 6.0 的源代码时，我在ArrayList 中找到了这两个方法。你看他们都是私有(private)的。但是经过搜索，我没有找到任何其他方法调用它们中的任何一个。我也考虑过本地方法，但仍然找不到。这两个方法看似处理IO，但从来没有被调用过。
那么，我的问题是，它们是如何工作的？还有其他调用私有(private)方法的方法吗？
/**
* Save the state of the <tt>ArrayList</tt> instance to a stream (that is, serialize it).
*/
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException;
/**
* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is, deserialize it).
*/
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException;
这两个方法在可序列化类中用于自定义序列化(aka Customize the Default Protocol)。
文章正文:
There is, however, a strange yet crafty solution. By using a built-in
feature of the serialization mechanism, developers can enhance the
normal process by providing two methods inside their class files.
Those methods are:
- private void writeObject(ObjectOutputStream out) throws IOException;
- private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException;
Notice that both methods are (and must be) declared private, proving
that neither method is inherited and overridden or overloaded. The
trick here is that the virtual machine will automatically check to see
if either method is declared during the corresponding method call. The
virtual machine can call private methods of your class whenever it
wants but no other objects can.