Package org.apache.commons.collections4.bloomfilter

Interface CellProducer

All Superinterfaces:
IndexProducer
All Known Subinterfaces:
CountingBloomFilter
All Known Implementing Classes:
ArrayCountingBloomFilter
Functional Interface:
This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
@FunctionalInterface public interface CellProducer extends IndexProducer
Some Bloom filter implementations use a count rather than a bit flag. The term Cell is used to refer to these counts and their associated index. This class is the equivalent of the index producer except that it produces cells.

Note that a CellProducer must not return duplicate indices and must be ordered.

Implementations must guarantee that:

  • The IndexProducer implementation returns unique ordered indices.
  • The cells are produced in IndexProducer order.
  • For every value produced by the IndexProducer there will be only one matching cell produced by the CellProducer.
  • The CellProducer will not generate cells with indices that are not output by the IndexProducer.
  • The IndexProducer will not generate indices that have a zero count for the cell.
Since:
4.5

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Interface
    Description
    static interface 
    CellProducer.CellConsumer
    Represents an operation that accepts an <index, count> pair.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    forEachCell(CellProducer.CellConsumer consumer)
    Performs the given action for each cell where the cell count is non-zero.
    default boolean
    forEachIndex(IntPredicate predicate)
    The default implementation returns distinct and ordered indices for all cells with a non-zero count.
    static CellProducer
    from(IndexProducer producer)
    Creates a CellProducer from an IndexProducer.
    default IndexProducer
    uniqueIndices()
    Creates an IndexProducer comprising the unique indices for this producer.

    Methods inherited from interface org.apache.commons.collections4.bloomfilter.IndexProducer

    asIndexArray

  • Method Details

    • from

      static CellProducer from(IndexProducer producer)
      Creates a CellProducer from an IndexProducer.

      Note the following properties:

      • Each index returned from the IndexProducer is assumed to have a cell value of 1.
      • The CellProducer aggregates duplicate indices from the IndexProducer.

      A CellProducer that outputs the mapping [(1,2),(2,3),(3,1)] can be created from many combinations of indices including: 

       [1, 1, 2, 2, 2, 3]
 [1, 3, 1, 2, 2, 2]
 [3, 2, 1, 2, 1, 2]
 ...
      Parameters:
      producer - An index producer.
      Returns:
      A CellProducer with the same indices as the IndexProducer.

    • forEachCell

      boolean forEachCell(CellProducer.CellConsumer consumer)
      Performs the given action for each cell where the cell count is non-zero.

      Some Bloom filter implementations use a count rather than a bit flag. The term Cell is used to refer to these counts.

      Any exceptions thrown by the action are relayed to the caller. The consumer is applied to each cell. If the consumer returns false the execution is stopped, false is returned, and no further pairs are processed.

      Parameters:
      consumer - the action to be performed for each non-zero cell.
      Returns:
      true if all cells return true from consumer, false otherwise.
      Throws:
      NullPointerException - if the specified consumer is null

    • forEachIndex

      default boolean forEachIndex(IntPredicate predicate)
      The default implementation returns distinct and ordered indices for all cells with a non-zero count.
      Specified by:
      forEachIndex in interface IndexProducer
      Parameters:
      predicate - the action to be performed for each non-zero bit index.
      Returns:
      true if all indexes return true from consumer, false otherwise.

    • uniqueIndices

      default IndexProducer uniqueIndices()
      Description copied from interface: IndexProducer
      Creates an IndexProducer comprising the unique indices for this producer.

      By default creates a new producer with some overhead to remove duplicates. IndexProducers that return unique indices by default should override this to return this.

      The default implementation will filter the indices from this instance and return them in ascending order.

      Specified by:
      uniqueIndices in interface IndexProducer
      Returns:
      the IndexProducer of unique values.