org.apache.lucene.search

## Class TermStatistics

- java.lang.Object
- - org.apache.lucene.search.TermStatistics

-     public class TermStatistics
      extends Object

  Contains statistics for a specific term

  This class holds statistics for this term across all documents for scoring purposes:

  - `docFreq`: number of documents this term occurs in.
  - `totalTermFreq`: number of tokens for this term.

  The following conditions are always true:

  - All statistics are positive integers: never zero or negative.
  - `docFreq` <= `totalTermFreq`
  - `docFreq` <= `sumDocFreq` of the collection
  - `totalTermFreq` <= `sumTotalTermFreq` of the collection

  Values may include statistics on deleted documents that have not yet been merged away.

  Be careful when performing calculations on these values because they are represented as 64-bit integer values, you may need to cast to `double` for your use.

  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `TermStatistics(BytesRef term, long docFreq, long totalTermFreq)` Creates statistics instance for a term.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `long` | `docFreq()` The number of documents this term occurs in.
    `BytesRef` | `term()` The term text.
    `String` | `toString()`
    `long` | `totalTermFreq()` The total number of occurrences of this term.

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

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

- - ### Constructor Detail

    - #### TermStatistics

          public TermStatistics(BytesRef term,
                                long docFreq,
                                long totalTermFreq)

      Creates statistics instance for a term.
      Parameters:
        `term` - Term bytes
        `docFreq` - number of documents containing the term in the collection.
        `totalTermFreq` - number of occurrences of the term in the collection.
      Throws:
        `NullPointerException` - if `term` is `null`.
        `IllegalArgumentException` - if `docFreq` is negative or zero.
        `IllegalArgumentException` - if `totalTermFreq` is less than `docFreq`.

  - ### Method Detail

    - #### term

          public final BytesRef term()

      The term text.

      This value is never `null`.

      Returns:
        term's text, not `null`

    - #### docFreq

          public final long docFreq()

      The number of documents this term occurs in.

      This is the document-frequency for the term: the count of documents where the term appears at least one time.

      This value is always a positive number, and never exceeds `totalTermFreq`. It also cannot exceed `CollectionStatistics.sumDocFreq()`.

      Returns:
        document frequency, in the range [1 .. `totalTermFreq()`]
      See Also:
        `TermsEnum.docFreq()`

    - #### totalTermFreq

          public final long totalTermFreq()

      The total number of occurrences of this term.

      This is the token count for the term: the number of times it appears in the field across all documents.

      This value is always a positive number, always at least `docFreq()`, and never exceeds `CollectionStatistics.sumTotalTermFreq()`.

      Returns:
        number of occurrences, in the range [`docFreq()` .. `CollectionStatistics.sumTotalTermFreq()`]
      See Also:
        `TermsEnum.totalTermFreq()`

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `Object`

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