public String[] deletedItemsNames(){
        if(!this.dataPreprocessed)this.preprocessData();
        if(this.nDeletedItems==0){
            System.out.println("Method - deletedItemsIndices: there are no deleted items; null returned");
            return null;
        }
        else{
            String[] nam = new String[this.nDeletedItems];
            for(int i=0; i<this.nDeletedItems; i++){
                nam[i] = originalItemNames[this.deletedItemsIndices[i]];
            }
            return nam;
        }
    }