Package org.apache.hadoop.hdfs.util

Class ReferenceCountMap<E extends ReferenceCountMap.ReferenceCounter>

java.lang.Object

org.apache.hadoop.hdfs.util.ReferenceCountMap<E>

@Private
@Evolving
public class ReferenceCountMap<E extends ReferenceCountMap.ReferenceCounter>
extends java.lang.Object

Class for de-duplication of instances.
Hold the references count to a single instance. If there are no references then the entry will be removed.
Type E should implement ReferenceCountMap.ReferenceCounter
Note: This class is NOT thread-safe.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	ReferenceCountMap.ReferenceCounter	Interface for the reference count holder

Constructor Summary

Constructors

Constructor	Description
ReferenceCountMap()

Method Summary

Modifier and Type	Method	Description
void	clear()	Clear the contents
org.apache.hadoop.thirdparty.com.google.common.collect.ImmutableList<E>	getEntries()	Get entries in the reference Map.
long	getReferenceCount(E key)	Get the reference count for the key
int	getUniqueElementsSize()	Get the number of unique elements
E	put(E key)	Add the reference.
void	remove(E key)	Delete the reference.

Methods inherited from class java.lang.Object

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

Constructor Detail

ReferenceCountMap

public ReferenceCountMap()

Method Detail

put

public E put(E key)

Add the reference. If the instance already present, just increase the reference count.

Parameters:

key - Key to put in reference map

Returns:

Referenced instance

remove

public void remove(E key)

Delete the reference. Decrease the reference count for the instance, if any. On all references removal delete the instance from the map.

Parameters:

key - Key to remove the reference.

getEntries

@VisibleForTesting
public org.apache.hadoop.thirdparty.com.google.common.collect.ImmutableList<E> getEntries()

Get entries in the reference Map.

Returns:

getReferenceCount

public long getReferenceCount(E key)

Get the reference count for the key

getUniqueElementsSize

public int getUniqueElementsSize()

Get the number of unique elements

clear

@VisibleForTesting
public void clear()

Clear the contents