question: protected List < ITEM_TYPE > selectFoldTestItems ( List < ITEM_TYPE > items , int nFolds , int fold ) { List < ITEM_TYPE > testItems = new ArrayList < ITEM_TYPE > ( ) ; for ( int i = 0 ; i < items . size ( ) ; ++ i ) { if ( i % nFolds == fold ) { testItems . add ( items . get ( i ) ) ; } } return testItems ; }
target:  Determines which items should be used for testing in one fold of a cross-validation. The default implementation includes every (nFolds)th item, but this may be overridden in subclasses.