TopScoreDocCollector (Lucene 3.6.2 API)
Keywords: org.apache.lucene.search.TopScoreDocCollector class

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## org.apache.lucene.search
Class TopScoreDocCollector

    java.lang.Object
      org.apache.lucene.search.Collector
          org.apache.lucene.search.TopDocsCollector<ScoreDoc>
              org.apache.lucene.search.TopScoreDocCollector

    public abstract class TopScoreDocCollector

extends TopDocsCollector<ScoreDoc>

A `Collector` implementation that collects the top-scoring hits, returning them as a `TopDocs`. This is used by `IndexSearcher` to implement `TopDocs`-based search. Hits are sorted by score descending and then (when the scores are tied) docID ascending. When you create an instance of this collector you should know in advance whether documents are going to be collected in doc Id order or not.

NOTE: The values `Float.NaN` and {Float#NEGATIVE_INFINITY} are not valid scores. This collector will not properly collect hits with such scores.

Field Summary

Fields inherited from class org.apache.lucene.search.TopDocsCollector
`EMPTY_TOPDOCS, pq, totalHits`

Method Summary
`static TopScoreDocCollector` | `create(int numHits, boolean docsScoredInOrder)` Creates a new `TopScoreDocCollector` given the number of hits to collect and whether documents are scored in order by the input `Scorer` to `setScorer(Scorer)`.
`static TopScoreDocCollector` | `create(int numHits, ScoreDoc after, boolean docsScoredInOrder)` Creates a new `TopScoreDocCollector` given the number of hits to collect, the bottom of the previous page, and whether documents are scored in order by the input `Scorer` to `setScorer(Scorer)`.
`protected TopDocs` | `newTopDocs(ScoreDoc[] results, int start)` Returns a `TopDocs` instance containing the given results.
`void` | `setNextReader(IndexReader reader, int base)` Called before collecting from each IndexReader.
`void` | `setScorer(Scorer scorer)` Called before successive calls to `Collector.collect(int)`.

Methods inherited from class org.apache.lucene.search.TopDocsCollector
`getTotalHits, populateResults, topDocs, topDocs, topDocs, topDocsSize`

Methods inherited from class org.apache.lucene.search.Collector
`acceptsDocsOutOfOrder, collect`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Method Detail

### create

    public static TopScoreDocCollector create(int numHits,
                                              boolean docsScoredInOrder)

  Creates a new `TopScoreDocCollector` given the number of hits to collect and whether documents are scored in order by the input `Scorer` to `setScorer(Scorer)`.

  NOTE: The instances returned by this method pre-allocate a full array of length `numHits`, and fill the array with sentinel objects.

### create

    public static TopScoreDocCollector create(int numHits,
                                              ScoreDoc after,
                                              boolean docsScoredInOrder)

  Creates a new `TopScoreDocCollector` given the number of hits to collect, the bottom of the previous page, and whether documents are scored in order by the input `Scorer` to `setScorer(Scorer)`.

  NOTE: The instances returned by this method pre-allocate a full array of length `numHits`, and fill the array with sentinel objects.

### newTopDocs

    protected TopDocs newTopDocs(ScoreDoc[] results,
                                 int start)

  Description copied from class: `TopDocsCollector`
  Returns a `TopDocs` instance containing the given results. If `results` is null it means there are no results to return, either because there were 0 calls to collect() or because the arguments to topDocs were invalid.

  Overrides:
    `newTopDocs` in class `TopDocsCollector<ScoreDoc>`

### setNextReader

    public void setNextReader(IndexReader reader,
                              int base)

  Description copied from class: `Collector`
  Called before collecting from each IndexReader. All doc ids in `Collector.collect(int)` will correspond to reader. Add docBase to the current IndexReaders internal document id to re-base ids in `Collector.collect(int)`.

  Specified by:
    `setNextReader` in class `Collector`
  Parameters:
    `reader` - next IndexReader

### setScorer

    public void setScorer(Scorer scorer)
                   throws IOException

  Description copied from class: `Collector`
  Called before successive calls to `Collector.collect(int)`. Implementations that need the score of the current document (passed-in to `Collector.collect(int)`), should save the passed-in Scorer and call scorer.score() when needed.

  Specified by:
    `setScorer` in class `Collector`
  Throws:
    `IOException`

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