In Exercise P9.16, add a method default Filter invert() to the Filter interface that yields a filter accepting exactly the objects that this filter rejects.

Data from Exercise P9.16,

Declare an interface Filter as follows:

public interface Filter { boolean accept(Object x); }

Add a Filter parameter to the average method of Section 9.6. Only objects that the filter accepts should be processed.  Demonstrate your modification by processing a collection of bank accounts, filtering out all accounts with balances less than $1,000.