private final void addToFront(HitDoc hitDoc) { // insert at front of cache
if (first == null) {
last = hitDoc;
} else {
first.prev = hitDoc;
}
hitDoc.next = first;
first = hitDoc;
hitDoc.prev = null;
numDocs++;
}
/**
* Returns the stored fields of the n<sup>th</sup> document in this set.
*
* <p>Documents are cached, so that repeated requests for the same element may return the same
* Document object.
*
* @throws CorruptIndexException if the index is corrupt
* @throws IOException if there is a low-level IO error
*/
public final Document doc(int n) throws CorruptIndexException, IOException {
HitDoc hitDoc = hitDoc(n);
// Update LRU cache of documents
remove(hitDoc); // remove from list, if there
addToFront(hitDoc); // add to front of list
if (numDocs > maxDocs) { // if cache is full
HitDoc oldLast = last;
remove(last); // flush last
oldLast.doc = null; // let doc get gc'd
}
if (hitDoc.doc == null) {
hitDoc.doc = searcher.doc(hitDoc.id); // cache miss: read document
}
return hitDoc.doc;
}