Importantly, the SerializationClass class has a reference to its defining class loader, and so it cannot be completely dereferenced either.

重要的是，serializationclass类有一个到其定义类装入器的引用，所以它也不可能完整地取消引用。

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Each class loader also keeps a reference to a parent class loader, defining a tree of class loaders with the bootstrap loader at the root.

每个类装入器还保留对父类装入器的引用，这样就定义了类装入器树，树根为引导程序装入器。

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