public void addFeature(List<VSMVector> pageVectors) {
            for (VSMVector vsm : pageVectors) {
                Iterator<VSMElement> it = vsm.getElements();
                while (it.hasNext()) {
                    VSMElement element = it.next();
                    String word = element.getWord();
                    VSMElement value = docFrequencies.get(word);
                    if (value == null) {
                        docFrequencies.put(word, new VSMElement(word, 1));
                    } else {
                        double count = value.getWeight() + 1;
                        docFrequencies.put(word, new VSMElement(word, count));
                    }
                }
            }
        }
Selects best features based on document frequency.
ache/src/main/java/achecrawler/target/classifier/TargetClassifierBuilder.java