com.hazelcast.map.eviction

Class MapEvictionPolicy<K,V>

java.lang.Object

com.hazelcast.map.eviction.MapEvictionPolicy<K,V>

Type Parameters:

K - the type of keys maintained by IMap

V - the type of mapped values

All Implemented Interfaces:

Comparator<EntryView<K,V>>

Direct Known Subclasses:

LFUEvictionPolicy, LRUEvictionPolicy, RandomEvictionPolicy

public abstract class MapEvictionPolicy<K,V>
extends Object
implements Comparator<EntryView<K,V>>

An eviction policy takes its role after the decision that a map needs to free some memory according to one of MaxSizePolicies and it helps to find most appropriate entries to remove. IMap has out-of-the-box eviction policies like LRUEvictionPolicy, LFUEvictionPolicy and RandomEvictionPolicy but if there is a need to define another eviction policy, users can introduce a custom one by extending MapEvictionPolicy class.

Implementation:

compare(EntryView, EntryView) method must be implemented to provide an ascending order of entries. Because internal eviction algorithm will evict the smallest entry from IMap

Since:

3.7

See Also:

LRUEvictionPolicy, LFUEvictionPolicy, RandomEvictionPolicy

Constructor Summary

Constructors

Constructor and Description
MapEvictionPolicy()

Method Summary

Modifier and Type	Method and Description
abstract int	compare(EntryView<K,V> entryView1, EntryView<K,V> entryView2)

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, equals, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Constructor Detail

MapEvictionPolicy

public MapEvictionPolicy()

Method Detail

compare

public abstract int compare(EntryView<K,V> entryView1,
                            EntryView<K,V> entryView2)

If you prefer to evict the 1st entry then return negative number, if the 2nd entry is a better candidate then return a positive number or return 0 if both entries are equally good candidates for eviction

Specified by:

compare in interface Comparator<EntryView<K,V>>