Method retainOccurrencesImpl

output/java_guava/1.4.17/Multisets.java:711–729

Delegate implementation which cares about the element type.

(Multiset<E> multisetToModify, Multiset<?> occurrencesToRetain)

   */

  private static <E> boolean retainOccurrencesImpl(Multiset<E> multisetToModify, Multiset<?> occurrencesToRetain) {
    checkNotNull(multisetToModify);
    checkNotNull(occurrencesToRetain);
    // Avoiding ConcurrentModificationExceptions is tricky.
    Iterator<Entry<E>> entryIterator = multisetToModify.entrySet().iterator();
    boolean changed = false;
    while (entryIterator.hasNext()) {
      Entry<E> entry = entryIterator.next();
      int retainCount = occurrencesToRetain.count(entry.getElement());
      if (retainCount == 0) {
        entryIterator.remove();
        changed = true;
      } else if (retainCount < entry.getCount()) {
        multisetToModify.setCount(entry.getElement(), retainCount);
        changed = true;
      }
    }
    return changed;
  }

  /**
   * For each occurrence of an element {@code e} in {@code occurrencesToRemove},