@Override
  public boolean removeAll(Collection collection) {
    boolean changed = false;
    int size = collection.size();

    Iterator it = collection.iterator();
    while (size-- > 0) {
      if (remove(it.next())) {
        changed = true;
      }
    }
    return changed;
  }
Removes all of the elements in <tt>collection</tt> from the set.

@param collection a <code>Collection</code> value
@return true if the set was modified by the remove all operation.
geode-core/src/main/java/org/apache/geode/cache/query/internal/index/HashIndexSet.java