Explain what a NullPointerException is and how it can arise.

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Explain what a NullPointerException is and how it can arise.

Answer:  A NullPointerException is an exception that indicates that an operation was attempted on some object that is equal to null.  For instance, ChessPiece c; declares c to refer to a ChessPiece, but c has not yet been instantiated, so any message passed to c at this point will cause a NullPointerException.

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