org.apache.lucene.search

## Class TopScoreDocCollector

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

- All Implemented Interfaces:
    Collector

      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

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static TopScoreDocCollector` | `create(int numHits)` Creates a new `TopScoreDocCollector` given the number of hits to collect and whether documents are scored in order by the input `Scorer` to `LeafCollector.setScorer(Scorer)`.
    `static TopScoreDocCollector` | `create(int numHits, ScoreDoc after)` 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 `LeafCollector.setScorer(Scorer)`.
    `boolean` | `needsScores()` Indicates if document scores are needed by this collector.
    `protected TopDocs` | `newTopDocs(ScoreDoc[] results, int start)` Returns a `TopDocs` instance containing the given results.

    - ### Methods inherited from class org.apache.lucene.search.TopDocsCollector

      `getTotalHits, populateResults, topDocs, topDocs, topDocs, topDocsSize`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

    - ### Methods inherited from interface org.apache.lucene.search.Collector

      `getLeafCollector`

- - ### Method Detail

    - #### create

          public static TopScoreDocCollector create(int numHits)

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

      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 `LeafCollector.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>`

    - #### needsScores

          public boolean needsScores()

      Description copied from interface: `Collector`
      Indicates if document scores are needed by this collector.
      Returns:
        `true` if scores are needed.

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