cz.ues.platform.commons.jmx

Class LimitedSetStatistic<K>

java.lang.Object

cz.ues.platform.commons.jmx.LimitedSetStatistic<K>

Direct Known Subclasses:

ThroughputStatistic

public class LimitedSetStatistic<K>
extends java.lang.Object

LimitedSetStatistic - class that is similar to Set - but it is limited in size and removes "the weakest" objects when needed (so it is slightly similar to a cache). Every entry holds a counter and a time of last usage. When set grows to the maximum size (limit + buffer size specified during construction of the Set), the buffer is cleared. It means that only limit objects remains in the Set. The 50% limit of the best object by counter are preserved. The remaining are sorted by the last time of usage and the weakest are removed from the Set.
It is usefull for every JMX statistic that holds a String key with a counter (e.g. number of execution of a script by the script filename) and which is not limited in size by default (e.g. there is defacto unlimited numbers of possible script filenames, so we cannot use regular Set, because it could lead to a still-growing Set aka memory leak).
This Class is thread safe.

Since:

UES6-00

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	LimitedSetStatistic.CountComparator<KK>
private static class	LimitedSetStatistic.TimeComparator<KK>

Field Summary

Fields

Modifier and Type	Field and Description
private int	bufferSize
private int	limit
private java.util.Map<K,LimitedSetStatisticEntry<K>>	map

Constructor Summary

Constructors

Constructor and Description
LimitedSetStatistic(int aLimit, int aBufferSize) Creates a new instance of LimitedSetStatistic.

Method Summary

Methods

Modifier and Type	Method and Description
void	clear() Removes all elements from this Set.
protected LimitedSetStatisticEntry<K>	createStatisticEntry(K aKey)
LimitedSetStatisticEntry<K>	getElement(K aKey) Returns an element by its key.
java.util.List<? extends LimitedSetStatisticEntry<K>>	getTopElements(int aCount) Returns top aCount elements sorted desc. by the counter.
void	inc(K aKey) Increase the counter of an entry by 1.
void	inc(K aKey, int aAmount) Increases the counter of an entry by an aAmount.
void	inc(K aKey, long aAmount)
private LimitedSetStatisticEntry<K>	prepareEntryToInsert(K aKey)
void	setCounter(K aKey, long aCounter) Sets the counter of an entry.
private void	shrinkMapToLimit() Clears the buffer.

Methods inherited from class java.lang.Object

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

Field Detail

map

private map

limit

private limit

bufferSize

private bufferSize

Constructor Detail

LimitedSetStatistic

public LimitedSetStatistic(int aLimit,
int aBufferSize)

Creates a new instance of LimitedSetStatistic.

Parameters:

aLimit - a number of objects in Set that is assured not to be removed.

aBufferSize - a number of objects in Set that could be inserted before Set is shrinked to aLimit.

Since:

UES6-00

Method Detail

getTopElements

public java.util.List<? extends LimitedSetStatisticEntry<K>> getTopElements(int aCount)

Returns top aCount elements sorted desc. by the counter.

Parameters:

aCount - Number of elements to return. Returns smaller List if there is not enough elements.

Returns:

list of top elements by an entry counter

Since:

UES6-00

inc

public void inc(K aKey)

Increase the counter of an entry by 1. Creates the new entry in this Set if it is not contained yet.

Parameters:

aKey - an entry key

Since:

UES6-00

setCounter

public void setCounter(K aKey,
long aCounter)

Sets the counter of an entry. Creates the new entry in this Set if it is not contained yet.

Parameters:

aKey - an entry key

aCounter - the counter value to be set

Since:

UES6-00

getElement

public LimitedSetStatisticEntry<K> getElement(K aKey)

Returns an element by its key. Null if it is not in the Set.

Parameters:

aKey - a key of an element

Returns:

element an element with aKey key from this Set

Since:

UES6-00

inc

public void inc(K aKey,
int aAmount)

Increases the counter of an entry by an aAmount. Creates the new entry in this Set if it is not contained yet.

Parameters:

aKey - an entry key

aAmount -

Since:

UES6-00

inc

public void inc(K aKey,
long aAmount)

prepareEntryToInsert

private LimitedSetStatisticEntry<K> prepareEntryToInsert(K aKey)

createStatisticEntry

protected LimitedSetStatisticEntry<K> createStatisticEntry(K aKey)

clear

public void clear()

Removes all elements from this Set.

Since:

UES6-00

shrinkMapToLimit

private void shrinkMapToLimit()

Clears the buffer.