// Using subclass methods.
// In this case, MultiFilter.addNever() is implemented
// in MultiFilter but not in the base FileNameFilter.

// oops. f. has no addNever method.
FileNameFilter f = new MultiFilter();
f.addNever( never );

// should read
FileNameFilter f = new MultiFilter();
((MultiFilter)f).addNever( never );

// or more efficiently
MultiFilter f = new MultiFilter();
f.addNever( never );