Class BloomFilter<T>

  • Type Parameters:
    T - the type of instances that the BloomFilter accepts
    All Implemented Interfaces:
    Predicate<T>, Serializable


    @Beta
    public final class BloomFilter<T>
    extends Object
    implements Predicate<T>, Serializable
    A Bloom filter for instances of T. A Bloom filter offers an approximate containment test with one-sided error: if it claims that an element is contained in it, this might be in error, but if it claims that an element is not contained in it, then this is definitely true.

    If you are unfamiliar with Bloom filters, this nice tutorial may help you understand how they work.

    The false positive probability (FPP) of a bloom filter is defined as the probability that mightContain(Object) will erroneously return true for an object that has not actually been put in the BloomFilter.

    Bloom filters are serializable. They also support a more compact serial representation via the writeTo(java.io.OutputStream) and readFrom(java.io.InputStream, com.google.common.hash.Funnel<T>) methods. Both serialized forms will continue to be supported by future versions of this library. However, serial forms generated by newer versions of the code may not be readable by older versions of the code (e.g., a serialized bloom filter generated today may not be readable by a binary that was compiled 6 months ago).

    Since:
    11.0
    See Also:
    Serialized Form
    • Method Summary

      Modifier and Type Method and Description
      boolean apply(T input)
      Deprecated. 
      Provided only to satisfy the Predicate interface; use mightContain(T) instead.
      BloomFilter<T> copy()
      Creates a new BloomFilter that's a copy of this instance.
      static <T> BloomFilter<T> create(Funnel<? super T> funnel, int expectedInsertions)
      Creates a BloomFilter with the expected number of insertions and a default expected false positive probability of 3%.
      static <T> BloomFilter<T> create(Funnel<? super T> funnel, int expectedInsertions, double fpp)
      Creates a BloomFilter with the expected number of insertions and expected false positive probability.
      static <T> BloomFilter<T> create(Funnel<? super T> funnel, long expectedInsertions)
      Creates a BloomFilter with the expected number of insertions and a default expected false positive probability of 3%.
      static <T> BloomFilter<T> create(Funnel<? super T> funnel, long expectedInsertions, double fpp)
      Creates a BloomFilter with the expected number of insertions and expected false positive probability.
      boolean equals(Object object)
      Indicates whether another object is equal to this predicate.
      double expectedFpp()
      Returns the probability that mightContain(Object) will erroneously return true for an object that has not actually been put in the BloomFilter.
      int hashCode()
       
      boolean isCompatible(BloomFilter<T> that)
      Determines whether a given bloom filter is compatible with this bloom filter.
      boolean mightContain(T object)
      Returns true if the element might have been put in this Bloom filter, false if this is definitely not the case.
      boolean put(T object)
      Puts an element into this BloomFilter.
      void putAll(BloomFilter<T> that)
      Combines this bloom filter with another bloom filter by performing a bitwise OR of the underlying data.
      static <T> BloomFilter<T> readFrom(InputStream in, Funnel<T> funnel)
      Reads a byte stream, which was written by writeTo(OutputStream), into a BloomFilter<T>.
      void writeTo(OutputStream out)
      Writes this BloomFilter to an output stream, with a custom format (not Java serialization).
    • Method Detail

      • copy

        public BloomFilter<T> copy()
        Creates a new BloomFilter that's a copy of this instance. The new instance is equal to this instance but shares no mutable state.
        Since:
        12.0
      • mightContain

        public boolean mightContain(T object)
        Returns true if the element might have been put in this Bloom filter, false if this is definitely not the case.
      • apply

        @Deprecated
        public boolean apply(T input)
        Deprecated.  Provided only to satisfy the Predicate interface; use mightContain(T) instead.
        Description copied from interface: Predicate
        Returns the result of applying this predicate to input. This method is generally expected, but not absolutely required, to have the following properties:
        • Its execution does not cause any observable side effects.
        • The computation is consistent with equals; that is, Objects.equal(a, b) implies that predicate.apply(a) == predicate.apply(b)).
      • put

        public boolean put(T object)
        Puts an element into this BloomFilter. Ensures that subsequent invocations of mightContain(Object) with the same element will always return true.
        Returns:
        true if the bloom filter's bits changed as a result of this operation. If the bits changed, this is definitely the first time object has been added to the filter. If the bits haven't changed, this might be the first time object has been added to the filter. Note that put(t) always returns the opposite result to what mightContain(t) would have returned at the time it is called."
        Since:
        12.0 (present in 11.0 with void return type})
      • expectedFpp

        public double expectedFpp()
        Returns the probability that mightContain(Object) will erroneously return true for an object that has not actually been put in the BloomFilter.

        Ideally, this number should be close to the fpp parameter passed in create(Funnel, int, double), or smaller. If it is significantly higher, it is usually the case that too many elements (more than expected) have been put in the BloomFilter, degenerating it.

        Since:
        14.0 (since 11.0 as expectedFalsePositiveProbability())
      • isCompatible

        public boolean isCompatible(BloomFilter<T> that)
        Determines whether a given bloom filter is compatible with this bloom filter. For two bloom filters to be compatible, they must:
        • not be the same instance
        • have the same number of hash functions
        • have the same bit size
        • have the same strategy
        • have equal funnels
          Parameters:
          that - The bloom filter to check for compatibility.
          Since:
          15.0
        • putAll

          public void putAll(BloomFilter<T> that)
          Combines this bloom filter with another bloom filter by performing a bitwise OR of the underlying data. The mutations happen to this instance. Callers must ensure the bloom filters are appropriately sized to avoid saturating them.
          Parameters:
          that - The bloom filter to combine this bloom filter with. It is not mutated.
          Throws:
          IllegalArgumentException - if isCompatible(that) == false
          Since:
          15.0
        • equals

          public boolean equals(Object object)
          Description copied from interface: Predicate
          Indicates whether another object is equal to this predicate.

          Most implementations will have no reason to override the behavior of Object.equals(java.lang.Object). However, an implementation may also choose to return true whenever object is a Predicate that it considers interchangeable with this one. "Interchangeable" typically means that this.apply(t) == that.apply(t) for all t of type T). Note that a false result from this method does not imply that the predicates are known not to be interchangeable.

        • hashCode

          public int hashCode()
        • create

          public static <T> BloomFilter<T> create(Funnel<? super T> funnel,
                                                  int expectedInsertions,
                                                  double fpp)
          Creates a BloomFilter with the expected number of insertions and expected false positive probability.

          Note that overflowing a BloomFilter with significantly more elements than specified, will result in its saturation, and a sharp deterioration of its false positive probability.

          The constructed BloomFilter<T> will be serializable if the provided Funnel<T> is.

          It is recommended that the funnel be implemented as a Java enum. This has the benefit of ensuring proper serialization and deserialization, which is important since equals(java.lang.Object) also relies on object identity of funnels.

          Parameters:
          funnel - the funnel of T's that the constructed BloomFilter<T> will use
          expectedInsertions - the number of expected insertions to the constructed BloomFilter<T>; must be positive
          fpp - the desired false positive probability (must be positive and less than 1.0)
          Returns:
          a BloomFilter
        • create

          public static <T> BloomFilter<T> create(Funnel<? super T> funnel,
                                                  long expectedInsertions,
                                                  double fpp)
          Creates a BloomFilter with the expected number of insertions and expected false positive probability.

          Note that overflowing a BloomFilter with significantly more elements than specified, will result in its saturation, and a sharp deterioration of its false positive probability.

          The constructed BloomFilter<T> will be serializable if the provided Funnel<T> is.

          It is recommended that the funnel be implemented as a Java enum. This has the benefit of ensuring proper serialization and deserialization, which is important since equals(java.lang.Object) also relies on object identity of funnels.

          Parameters:
          funnel - the funnel of T's that the constructed BloomFilter<T> will use
          expectedInsertions - the number of expected insertions to the constructed BloomFilter<T>; must be positive
          fpp - the desired false positive probability (must be positive and less than 1.0)
          Returns:
          a BloomFilter
          Since:
          19.0
        • create

          public static <T> BloomFilter<T> create(Funnel<? super T> funnel,
                                                  int expectedInsertions)
          Creates a BloomFilter with the expected number of insertions and a default expected false positive probability of 3%.

          Note that overflowing a BloomFilter with significantly more elements than specified, will result in its saturation, and a sharp deterioration of its false positive probability.

          The constructed BloomFilter<T> will be serializable if the provided Funnel<T> is.

          It is recommended that the funnel be implemented as a Java enum. This has the benefit of ensuring proper serialization and deserialization, which is important since equals(java.lang.Object) also relies on object identity of funnels.

          Parameters:
          funnel - the funnel of T's that the constructed BloomFilter<T> will use
          expectedInsertions - the number of expected insertions to the constructed BloomFilter<T>; must be positive
          Returns:
          a BloomFilter
        • create

          public static <T> BloomFilter<T> create(Funnel<? super T> funnel,
                                                  long expectedInsertions)
          Creates a BloomFilter with the expected number of insertions and a default expected false positive probability of 3%.

          Note that overflowing a BloomFilter with significantly more elements than specified, will result in its saturation, and a sharp deterioration of its false positive probability.

          The constructed BloomFilter<T> will be serializable if the provided Funnel<T> is.

          It is recommended that the funnel be implemented as a Java enum. This has the benefit of ensuring proper serialization and deserialization, which is important since equals(java.lang.Object) also relies on object identity of funnels.

          Parameters:
          funnel - the funnel of T's that the constructed BloomFilter<T> will use
          expectedInsertions - the number of expected insertions to the constructed BloomFilter<T>; must be positive
          Returns:
          a BloomFilter
          Since:
          19.0
        • writeTo

          public void writeTo(OutputStream out)
                       throws IOException
          Writes this BloomFilter to an output stream, with a custom format (not Java serialization). This has been measured to save at least 400 bytes compared to regular serialization.

          Use readFrom(InputStream, Funnel) to reconstruct the written BloomFilter.

          Throws:
          IOException
        • readFrom

          public static <T> BloomFilter<T> readFrom(InputStream in,
                                                    Funnel<T> funnel)
                                             throws IOException
          Reads a byte stream, which was written by writeTo(OutputStream), into a BloomFilter<T>. The Funnel to be used is not encoded in the stream, so it must be provided here. Warning: the funnel provided must behave identically to the one used to populate the original Bloom filter!
          Throws:
          IOException - if the InputStream throws an IOException, or if its data does not appear to be a BloomFilter serialized using the writeTo(OutputStream) method.