com.stoyanr.evictor.queue

Class PriorityEvictionQueue<K,V>

java.lang.Object

com.stoyanr.evictor.queue.PriorityEvictionQueue<K,V>

Type Parameters:

K - the type of keys maintained by this map

V - the type of mapped values

All Implemented Interfaces:

EvictionQueue<K,V>

public class PriorityEvictionQueue<K,V>
extends Object
implements EvictionQueue<K,V>

An EvictionQueue which uses a Queue to store its entries. The queue should support priority queue semantics and the comparator PriorityEvictionQueue.EvictibleEntryComparator should always be used for comparing entries.

The interface used is Queue and not PriorityQueue since the most obvious concurrent implementation, PriorityBlockingQueue only conforms to the former interface. This allows passing a different queue implementation, as far as it is concurrent (thread-safe) and has priority semantics.

Author:

Stoyan Rachev

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PriorityEvictionQueue.EvictibleEntryComparator<K,V> A comparator that compares EvictibleEntry instances based on their eviction time.

Constructor Summary

Constructors

Constructor and Description
PriorityEvictionQueue(int initialCapacity) Creates a priority eviction queue with a PriorityBlockingQueue with the specified initial capacity.
PriorityEvictionQueue(Queue<EvictibleEntry<K,V>> queue) Creates a priority eviction queue with the specified queue.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	evictEntries() Evicts all entries that have expired from their maps and removes them from the queue.
long	getNextEvictionTime() Returns the next eviction time of all entries contained in the queue, or 0 if the queue is empty.
boolean	hasEntries() Returns true if this queue contains any entries.
void	putEntry(EvictibleEntry<K,V> e) Puts the specified evictible entry into the queue.
void	removeEntry(EvictibleEntry<K,V> e) Removes the specified evictible entry from the queue.

Methods inherited from class java.lang.Object

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

Constructor Detail

PriorityEvictionQueue

public PriorityEvictionQueue(int initialCapacity)

Creates a priority eviction queue with a PriorityBlockingQueue with the specified initial capacity.

Parameters:

initialCapacity - the initial capacity

Throws:

IllegalArgumentException - if initial capacity is less than 1

PriorityEvictionQueue

public PriorityEvictionQueue(Queue<EvictibleEntry<K,V>> queue)

Creates a priority eviction queue with the specified queue.

Parameters:

queue - the queue to be used

Throws:

NullPointerException - if the queue is null

Method Detail

hasEntries

public boolean hasEntries()

Returns true if this queue contains any entries.

This implementation simply returns true if the queue is non-empty and vice versa.

Specified by:

hasEntries in interface EvictionQueue<K,V>

Returns:

true if this queue contains any entries

getNextEvictionTime

public long getNextEvictionTime()

Returns the next eviction time of all entries contained in the queue, or 0 if the queue is empty. Since the queue is sorted by the entries eviction time, this is the eviction time of the first entry (head).

This implementation simply returns the eviction time of the first entry in the queue if it is non-empty, or 0 otherwise.

Specified by:

getNextEvictionTime in interface EvictionQueue<K,V>

Returns:

the next eviction time of all entries contained in the queue, or 0 if the queue is empty

putEntry

public void putEntry(EvictibleEntry<K,V> e)

Puts the specified evictible entry into the queue.

This implementation simply invokes the add method on the queue.

Specified by:

putEntry in interface EvictionQueue<K,V>

Parameters:

e - the entry to be put into the queue.

removeEntry

public void removeEntry(EvictibleEntry<K,V> e)

Removes the specified evictible entry from the queue.

This implementation simply invokes the remove method on the queue.

Specified by:

removeEntry in interface EvictionQueue<K,V>

Parameters:

e - the entry to be removed from the queue.

evictEntries

public boolean evictEntries()

Evicts all entries that have expired from their maps and removes them from the queue.

This implementation uses the peek and poll method on the queue repeatedly to find and remove all entries that should be evicted, evicting them via their evict method.

Specified by:

evictEntries in interface EvictionQueue<K,V>

Returns:

true if any entries have been evicted