T
 the type of instances that the BloomFilter
accepts@Beta public final class BloomFilter<T> extends Object implements Predicate<T>, Serializable
T
. A Bloom filter offers an approximate containment test
with onesided 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
.
Modifier and Type  Method and Description 

boolean 
apply(T input)
Equivalent to
mightContain(T) ; provided only to satisfy the Predicate interface. 
BloomFilter<T> 
copy()
Creates a new
BloomFilter that's a copy of this instance. 
static <T> BloomFilter<T> 
create(Funnel<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<T> funnel,
int expectedInsertions,
double fpp)
Creates a
BloomFilter with the expected number of
insertions and expected false positive probability. 
boolean 
equals(Object object)
Indicates whether some other object is "equal to" this one.

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()
Returns a hash code value for the object.

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.

public BloomFilter<T> copy()
BloomFilter
that's a copy of this instance. The new instance is equal to
this instance but shares no mutable state.public boolean mightContain(T object)
true
if the element might have been put in this Bloom filter,
false
if this is definitely not the case.public boolean apply(T input)
mightContain(T)
; provided only to satisfy the Predicate
interface.
When using a reference of type BloomFilter
, always invoke mightContain(T)
directly instead.public boolean put(T object)
BloomFilter
. Ensures that subsequent invocations of
mightContain(Object)
with the same element will always return true
.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."void
return type})public double expectedFpp()
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.
public boolean isCompatible(BloomFilter<T> that)
that
 The bloom filter to check for compatibility.public void putAll(BloomFilter<T> that)
that
 The bloom filter to combine this bloom filter with. It is not mutated.IllegalArgumentException
 if isCompatible(that) == false
public boolean equals(@Nullable Object object)
java.lang.Object
The equals
method implements an equivalence relation
on nonnull object references:
x
, x.equals(x)
should return
true
.
x
and y
, x.equals(y)
should return true
if and only if
y.equals(x)
returns true
.
x
, y
, and z
, if
x.equals(y)
returns true
and
y.equals(z)
returns true
, then
x.equals(z)
should return true
.
x
and y
, multiple invocations of
x.equals(y)
consistently return true
or consistently return false
, provided no
information used in equals
comparisons on the
objects is modified.
x
,
x.equals(null)
should return false
.
The equals
method for class Object
implements
the most discriminating possible equivalence relation on objects;
that is, for any nonnull reference values x
and
y
, this method returns true
if and only
if x
and y
refer to the same object
(x == y
has the value true
).
Note that it is generally necessary to override the hashCode
method whenever this method is overridden, so as to maintain the
general contract for the hashCode
method, which states
that equal objects must have equal hash codes.
public int hashCode()
java.lang.Object
HashMap
.
The general contract of hashCode
is:
hashCode
method
must consistently return the same integer, provided no information
used in equals
comparisons on the object is modified.
This integer need not remain consistent from one execution of an
application to another execution of the same application.
equals(Object)
method, then calling the hashCode
method on each of
the two objects must produce the same integer result.
Object.equals(java.lang.Object)
method, then calling the hashCode
method on each of the
two objects must produce distinct integer results. However, the
programmer should be aware that producing distinct integer results
for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by
class Object
does return distinct integers for distinct
objects. (This is typically implemented by converting the internal
address of the object into an integer, but this implementation
technique is not required by the
Java^{TM} programming language.)
hashCode
in class Object
Object.equals(java.lang.Object)
,
System.identityHashCode(java.lang.Object)
public static <T> BloomFilter<T> create(Funnel<T> funnel, int expectedInsertions, double fpp)
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.
funnel
 the funnel of T's that the constructed BloomFilter<T>
will useexpectedInsertions
 the number of expected insertions to the constructed
BloomFilter<T>
; must be positivefpp
 the desired false positive probability (must be positive and less than 1.0)BloomFilter
public static <T> BloomFilter<T> create(Funnel<T> funnel, int expectedInsertions)
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.
funnel
 the funnel of T's that the constructed BloomFilter<T>
will useexpectedInsertions
 the number of expected insertions to the constructed
BloomFilter<T>
; must be positiveBloomFilter
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