Package org.apache.commons.collections4.bloomfilter

Class LayerManager<T extends BloomFilter<T>>

java.lang.Object

org.apache.commons.collections4.bloomfilter.LayerManager<T>

Type Parameters:

T - the BloomFilter type.

All Implemented Interfaces:

BloomFilterExtractor

public class LayerManager<T extends BloomFilter<T>>
extends Object
implements BloomFilterExtractor

Implementation of the methods to manage the layers in a layered Bloom filter.

The manager comprises a list of Bloom filters that are managed based on various rules. The last filter in the list is known as the target and is the filter into which merges are performed. The Layered manager utilizes three methods to manage the list.

• ExtendCheck - A Predicate that if true causes a new Bloom filter to be created as the new target.
• FilterSupplier - A Supplier that produces empty Bloom filters to be used as a new target.
• Cleanup - A Consumer of a LinkedList of BloomFilter that removes any expired or out dated filters from the list.

When extendCheck returns true the following steps are taken:

1. Cleanup is called
2. FilterSuplier is executed and the new filter added to the list as the target filter.

Since:

4.5.0-M1

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LayerManager.Builder<T extends BloomFilter<T>>	Builds new instances of LayerManager.
static final class	LayerManager.Cleanup	Static methods to create a Consumer of a List of BloomFilter perform tests on whether to reduce the collection of Bloom filters.
static final class	LayerManager.ExtendCheck	A collection of common ExtendCheck implementations to test whether to extend the depth of a LayerManager.

Field Summary

Fields

Modifier and Type	Field	Description
private final Predicate<LayerManager<T>>	extendCheck
private final Consumer<Deque<T>>	filterCleanup
private final LinkedList<T>	filters
private final Supplier<T>	filterSupplier

Constructor Summary

Constructors

Modifier	Constructor	Description
private	LayerManager(Supplier<T> filterSupplier, Predicate<LayerManager<T>> extendCheck, Consumer<Deque<T>> filterCleanup, boolean initialize)	Constructs a new instance.

Method Summary

Modifier and Type	Method	Description
private void	addFilter()	Adds a new Bloom filter to the list.
static <T extends BloomFilter<T>> LayerManager.Builder<T>	builder()	Creates a new Builder with defaults of LayerManager.ExtendCheck.neverAdvance() and LayerManager.Cleanup.noCleanup().
(package private) void	cleanup()	Forces execution the configured cleanup without creating a new filter except in cases where the cleanup removes all the layers.
final void	clear()	Removes all the filters from the layer manager, and sets up a new one as the target.
LayerManager<T>	copy()	Creates a deep copy of this LayerManager.
final T	first()	Gets the Bloom filter from the first layer.
final T	get(int depth)	Gets the Bloom filter at the specified depth.
final int	getDepth()	Gets the number of filters in the LayerManager.
final T	getTarget()	Gets the current target filter.
final T	last()	Gets the Bloom filter from the last layer.
(package private) void	next()	Forces an advance to the next depth.
boolean	processBloomFilters(Predicate<BloomFilter> bloomFilterPredicate)	Executes a Bloom filter Predicate on each Bloom filter in the manager in depth order.

Methods inherited from class java.lang.Object

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

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

asBloomFilterArray, flatten, processBloomFilterPair

Field Details

filters

private final LinkedList<T extends BloomFilter<T>> filters

filterCleanup

private final Consumer<Deque<T extends BloomFilter<T>>> filterCleanup

extendCheck

private final Predicate<LayerManager<T extends BloomFilter<T>>> extendCheck

filterSupplier

private final Supplier<T extends BloomFilter<T>> filterSupplier

Constructor Details

LayerManager

private LayerManager(Supplier<T> filterSupplier,
 Predicate<LayerManager<T>> extendCheck,
 Consumer<Deque<T>> filterCleanup,
 boolean initialize)

Constructs a new instance.

Parameters:

filterSupplier - the non-null supplier of new Bloom filters to add the the list when necessary.

extendCheck - The non-null predicate that checks if a new filter should be added to the list.

filterCleanup - the non-null consumer that removes any old filters from the list.

initialize - true if the filter list should be initialized.

Method Details

builder

public static <T extends BloomFilter<T>>
LayerManager.Builder<T> builder()

Creates a new Builder with defaults of LayerManager.ExtendCheck.neverAdvance() and LayerManager.Cleanup.noCleanup().

Type Parameters:

T - Type of BloomFilter.

Returns:

A builder.

See Also:

• LayerManager.ExtendCheck.neverAdvance()
• LayerManager.Cleanup.noCleanup()

addFilter

private void addFilter()

Adds a new Bloom filter to the list.

cleanup

void cleanup()

Forces execution the configured cleanup without creating a new filter except in cases where the cleanup removes all the layers.

See Also:

• LayerManager.Builder.setCleanup(Consumer)

clear

public final void clear()

Removes all the filters from the layer manager, and sets up a new one as the target.

copy

public LayerManager<T> copy()

Creates a deep copy of this LayerManager.

Filters in the copy are deep copies, not references, so changes in the copy are NOT reflected in the original.

The filterSupplier, extendCheck, and the filterCleanup are shared between the copy and this instance.

Returns:

a copy of this LayerManager.

first

public final T first()

Gets the Bloom filter from the first layer. No extension check is performed during this call.

Returns:

The Bloom filter from the first layer.

See Also:

• getTarget()

get

public final T get(int depth)

Gets the Bloom filter at the specified depth. The filter at depth 0 is the oldest filter.

Parameters:

depth - the depth at which the desired filter is to be found.

Returns:

the filter.

Throws:

NoSuchElementException - if depth is not in the range [0,filters.size())

getDepth

public final int getDepth()

Gets the number of filters in the LayerManager. In the default LayerManager implementation there is always at least one layer.

Returns:

the current depth.

getTarget

public final T getTarget()

Gets the current target filter. If a new filter should be created based on extendCheck it will be created before this method returns.

Returns:

the current target filter after any extension.

last

public final T last()

Gets the Bloom filter from the last layer. No extension check is performed during this call.

Returns:

The Bloom filter from the last layer.

See Also:

• getTarget()

next

void next()

Forces an advance to the next depth. This method will clean-up the current layers and generate a new filter layer. In most cases is it unnecessary to call this method directly.

Ths method is used within getTarget() when the configured ExtendCheck returns true.

See Also:

• LayerManager.Builder.setExtendCheck(Predicate)
• LayerManager.Builder.setCleanup(Consumer)

processBloomFilters

public boolean processBloomFilters(Predicate<BloomFilter> bloomFilterPredicate)

Executes a Bloom filter Predicate on each Bloom filter in the manager in depth order. Oldest filter first.

Specified by:

processBloomFilters in interface BloomFilterExtractor

Parameters:

bloomFilterPredicate - the predicate to evaluate each Bloom filter with.

Returns:

false when the a filter fails the predicate test. Returns true if all filters pass the test.