Package org.apache.commons.collections4.bloomfilter

Interface CellExtractor

  • All Superinterfaces:
    IndexExtractor
    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 CellExtractor
extends IndexExtractor
    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 extractor except that it produces cells.

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

    Implementations must guarantee that:

    • The IndexExtractor implementation returns unique ordered indices.
    • The cells are produced in IndexExtractor order.
    • For every value produced by the IndexExtractor there will be only one matching cell produced by the CellExtractor.
    • The CellExtractor will not generate cells with indices that are not output by the IndexExtractor.
    • The IndexExtractor will not generate indices that have a zero count for the cell.
    Since:
    4.5.0-M2

    • Method Detail

      • from

        static CellExtractor from​(IndexExtractor indexExtractor)
        Creates a CellExtractor from an IndexExtractor.

        Note the following properties:

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

        A CellExtractor 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:
        indexExtractor - An index indexExtractor.
        Returns:
        A CellExtractor with the same indices as the IndexExtractor.

      • processCells

        boolean processCells​(CellExtractor.CellPredicate 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:
        java.lang.NullPointerException - if the specified consumer is null

      • processIndices

        default boolean processIndices​(java.util.function.IntPredicate predicate)
        The default implementation returns distinct and ordered indices for all cells with a non-zero count.
        Specified by:
        processIndices in interface IndexExtractor
        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 IndexExtractor uniqueIndices()
        Description copied from interface: IndexExtractor
        Creates an IndexExtractor comprising the unique indices for this extractor.

        By default creates a new extractor with some overhead to remove duplicates. IndexExtractors 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 IndexExtractor
        Returns:
        the IndexExtractor of unique values.