com.github.benmanes.caffeine.cache.simulator.membership.bloom

Class BloomFilter

java.lang.Object

com.github.benmanes.caffeine.cache.simulator.membership.bloom.BloomFilter

All Implemented Interfaces:

Membership

public final class BloomFilter
extends Object
implements Membership

A Bloom filter is a space and time efficient probabilistic data structure that is used to test whether an element is a member of a set. False positives are possible, but false negatives are not. Elements can be added to the set, but not removed. The more elements that are added the higher the probability of false positives. While risking false positives, Bloom filters have a space advantage over other data structures for representing sets by not storing the items.

Constructor Summary

Constructors

Constructor and Description
BloomFilter() Creates a lazily initialized membership sketch, requiring ensureCapacity(long, double) be called when the expected number of insertions and the false positive probability have been determined.
BloomFilter(Config config) Creates a membership sketch based on the expected number of insertions and the false positive probability.

Method Summary

Modifier and Type	Method and Description
void	clear() Removes all of the elements from this collection.
void	ensureCapacity(@NonNegative long expectedInsertions, @NonNegative double fpp) Initializes and increases the capacity of this BloomFilter instance, if necessary, to ensure that it can accurately estimate the membership of elements given the expected number of insertions.
boolean	mightContain(long e) Returns if the element might have been put in this Bloom filter, false if this is definitely not the case.
boolean	put(long e) Puts an element into this collection so that subsequent queries with the same element will return true.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.github.benmanes.caffeine.cache.simulator.membership.Membership

disabled

Constructor Detail

BloomFilter

public BloomFilter()

Creates a lazily initialized membership sketch, requiring ensureCapacity(long, double) be called when the expected number of insertions and the false positive probability have been determined.

BloomFilter

public BloomFilter(Config config)

Creates a membership sketch based on the expected number of insertions and the false positive probability.

Method Detail

ensureCapacity

public void ensureCapacity(@NonNegative long expectedInsertions,
                           @NonNegative double fpp)

Initializes and increases the capacity of this BloomFilter instance, if necessary, to ensure that it can accurately estimate the membership of elements given the expected number of insertions. This operation forgets all previous memberships when resizing.

Parameters:

expectedInsertions - the number of expected insertions

fpp - the false positive probability, where 0.0 > fpp < 1.0

mightContain

public boolean mightContain(long e)

Description copied from interface: Membership

Returns if the element might have been put in this Bloom filter, false if this is definitely not the case.

Specified by:

mightContain in interface Membership

Parameters:

e - the element whose presence is to be tested

Returns:

if the element might be present

clear

public void clear()

Description copied from interface: Membership

Removes all of the elements from this collection.

Specified by:

clear in interface Membership

put

public boolean put(long e)

Description copied from interface: Membership

Puts an element into this collection so that subsequent queries with the same element will return true.

Specified by:

put in interface Membership

Parameters:

e - the element to add

Returns:

if the membership changed as a result of this operation