null has no type. It would have a vague type determined by whatever type the argument it was passed in as was suppossed to have. And I say vague, because it would be determinable, because the method already knows it's suppossed to be of that type.
Also, how would propose to get the type (if it had one)? The Class is the type, and since there is no way to dereference null (since it is a non-object) you can neither inspect the "class" field nor call the getClass() method (at least one of which instanceof also uses).
Java Programmer and Sun Systems Administrator
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Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.
--Brian Kernighan