NullpointerException in java.util.Hashtable.access$100 ???

Question

Hi folks.
I am trying to reconstruct a Hashtable using my own way of serialization/deserialization via Java Reflection. It works fine with most classes, but a reconstructed hashtable is seriously screwed up. After reconstruction, it is passed as an argument to a class that uses the putAll-Method, which causes a NullpointerException.
The root in the stack trace is java.util.Hashtable.access$100 at line 90 in java.util.Hashtable. Unfortunately, if you check the source of hashtable, you will only find the class header on this line.
Is it correct, that javac creates access-methods for inner classes? What are they used for?
Any idea what could cause this?

Answer 1

The exception happens whenever I try methods like toString, putAll or hashCode on the hashtable. The code of the deserialization is just a bit to complex to post here.
I have been able to track the problem down to the internal creation of creation of an iterator by the hashtable.
Here is the stack trace:
Exception in thread "main" java.lang.NullPointerException
at java.util.Hashtable.access$100(Hashtable.java:90)
at java.util.Hashtable$EntrySet.iterator(Hashtable.java:592)
at java.util.Collections$SynchronizedCollection.iterator(Collections.java:1096)
at java.util.Hashtable.hashCode(Hashtable.java:728)
at java.util.Hashtable.get(Hashtable.java:315)
at mypackage.serializer.XMLSerializer.buildXML(XMLSerializer.java:205)
at mypackage.serializer.XMLSerializer.buildXML(XMLSerializer.java:178)
at mypackage.serializer.XMLSerializer.main(XMLSerializer.java:66)