com.tangosol.util

Class SimpleMapIndex

java.lang.Object

com.tangosol.util.Base

com.tangosol.util.SimpleMapIndex

All Implemented Interfaces:

MapIndex

Direct Known Subclasses:

ConditionalIndex

public class SimpleMapIndex
extends Base
implements MapIndex

SimpleMapIndex is a MapIndex implementation used to correlate property values extracted from resource map entries with corresponding keys using what is commonly known as an Inverted Index algorithm.

Since:

Coherence 3.5

Author:

tb 2009.03.19

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SimpleMapIndex.IndexCalculator A stateful calculator used to calculate the cost of a homogeneous index (holding all values of a single type).

Nested classes/interfaces inherited from class com.tangosol.util.Base

Base.LoggingWriter, Base.StackFrame

Field Summary

Fields

Modifier and Type	Field and Description
protected ConfigurableCacheMap.UnitCalculator	m_calculator UnitCalculator used to estimate the cost of a value.
protected int	m_cLogMissingIdx The number of "missing inverse index" messages that have been logged.
protected Comparator	m_comparator Comparator used to sort the index.
protected BackingMapContext	m_ctx The context associated with this index.
protected long	m_cUnits The size footprint of the index, in units (as defined by the UnitCalculator).
protected ValueExtractor	m_extractor ValueExtractor object that this MapIndex uses to extract an indexable property value from a [converted] value stored in the resource map.
protected boolean	m_fForwardIndex Specifies whether or not this MapIndex supports a forward index.
protected boolean	m_fImmutableValues Specifies whether or not the index is based on the immutable values (e.g. keys).
protected boolean	m_fOrdered Specifies whether or not this MapIndex orders the contents of the indexed information.
protected boolean	m_fSplitCollection If a value extracted by the ValueExtractor is a Collection, this property specifies whether or not it should be treated as a Collection of contained attributes or indexed as a single composite attribute.
protected long	m_ldtLogMissingIdx The time at which the most recent logging of "missing inverse index" messages started.
protected Map	m_mapForward Map that contains the index values (forward index).
protected Map	m_mapInverse Map that contains the index contents (inverse index).
protected Set	m_setKeyExcluded A set of keys for the entries, which could not be included in the index.

Fields inherited from class com.tangosol.util.Base

LOG_ALWAYS, LOG_DEBUG, LOG_ERR, LOG_INFO, LOG_MAX, LOG_MIN, LOG_QUIET, LOG_WARN, POWER_0, POWER_G, POWER_K, POWER_M, POWER_T, UNIT_D, UNIT_H, UNIT_M, UNIT_MS, UNIT_NS, UNIT_S, UNIT_US

Fields inherited from interface com.tangosol.util.MapIndex

NO_VALUE

Constructor Summary

Constructors

Modifier	Constructor and Description
	SimpleMapIndex(ValueExtractor extractor, boolean fOrdered, Comparator comparator, BackingMapContext ctx) Construct an index for the given map.
protected	SimpleMapIndex(ValueExtractor extractor, boolean fOrdered, Comparator comparator, boolean fInit, BackingMapContext ctx) Construct an index for the given map.

Method Summary

Modifier and Type	Method and Description
protected void	addForwardEntry(Object oKey, Object oIxValueNew) Add a new mapping to the forward index map.
protected Object	addInverseCollectionMapping(Map mapIndex, Object oIxValue, Object oKey) Add new mappings from the elements of the given value to the given key in the supplied index.
protected Object	addInverseMapping(Map mapIndex, Object oIxValue, Object oKey) Add a new mapping from the given indexed value to the given key in the supplied index.
protected Object	addInverseMapping(Object oIxValue, Object oKey) Add a new mapping from the given indexed value to the given key in the inverse index.
protected Set	collectRemoved(Object oIxValueOld, Object oIxValueNew) Given that the old value is known to be a Collection or an array, collect all the enclosed elements that are not part of the new value.
void	delete(Map.Entry entry) Update this index in response to a remove operation on a cache.
protected void	deleteInternal(Map.Entry entry) Update this index in response to a remove operation on a cache.
protected Collection	ensureCollection(Object oValue) Return a Collection representation of the specified value, which could be a Collection, Object[], scalar, or NO_VALUE.
boolean	equals(Object o) Compares the specified object with this index for equality.
protected Object	extractNewValue(Map.Entry entry) Extract the "new" value from the specified entry.
protected Object	extractOldValue(MapTrigger.Entry entry) Extract the "old" value from the specified entry.
Object	get(Object oKey) Using the index information if possible, get the value associated with the specified key.
ConfigurableCacheMap.UnitCalculator	getCalculator() Return the UnitCalculator used to size this index's contents.
Comparator	getComparator() Get the Comparator used to sort the index.
protected Map.Entry	getForwardEntry(Object oKey) Get the forward index entry associated with the specified key.
Map	getIndexContents() Get the Map that contains the index contents.
long	getUnits() Retrieve the size of this index in units (as defined by the UnitCalculator).
ValueExtractor	getValueExtractor() Obtain the ValueExtractor object that the MapIndex uses to extract an indexable Object from a value stored in the indexed Map.
int	hashCode() Returns the hash code value for this MapIndex.
protected void	initialize(boolean fForwardIndex) Initialize the index's data structures.
void	insert(Map.Entry entry) Update this index in response to a insert operation on a cache.
protected void	insertInternal(Map.Entry entry) Update this index in response to a insert operation on a cache.
protected ConfigurableCacheMap.UnitCalculator	instantiateCalculator() Factory method used to create a new calculator.
protected Map	instantiateForwardIndex() Instantiate the forward index.
protected Map	instantiateInverseIndex(boolean fOrdered, Comparator comparator) Instantiate the inverse index.
protected Set	instantiateSet() Factory method used to create a new set containing the keys associated with a single value.
boolean	isForwardIndexSupported() Determine whether or not this SimpleMapIndex supports a forward index.
protected boolean	isKeyExcluded(Object oKey) Check if the entry with the given key is excluded from the index.
boolean	isOptimizeMV() Specifies whether an attempt will be made to search the forward map for an existing reference that is "equal" to the specified mutli-value and use it instead (if available) to reduce the index memory footprint.
boolean	isOrdered() Determine if the MapIndex orders the contents of the indexed information.
boolean	isPartial() Determine if indexed information for any entry in the indexed Map has been excluded from this index.
protected void	logMissingIdx(Object oIxValue, Object oKey) Log messages for missing inverse index.
protected void	onMappingAdded() Increase the size of the index by the size of an index map entry.
protected void	onMappingAdded(Object oValue, int cSize) Increase the size of the index by the estimated size of the specified added value.
protected void	onMappingRemoved() Decrease the size of the index by the size of an index map entry.
protected void	onMappingRemoved(Object oValue) Decrease the size of the index by the estimated size of the specified removed value.
protected void	removeForwardEntry(Object oKey) Remove the forward index entry for the specified key.
protected void	removeInverseMapping(Map mapIndex, Object oIxValue, Object oKey) Remove the mapping from the given indexed value to the given key from the supplied index.
protected void	removeInverseMapping(Object oIxValue, Object oKey) Remove the mapping from the given indexed value to the given key from the inverse index.
protected void	removeInverseMapping(Object oIxValue, Object oKey, Collection colIgnore) Remove the mapping from the given indexed value to the given key from the inverse index.
void	setOptimizeMV(boolean fOptimizeMV) For an indexed value that is a multi-value (Collection or array) this flag specifies whether an attempt should be made to search the forward map for an existing reference that is "equal" to the specified mutli-value and use it instead (if available) to reduce the index memory footprint.
protected void	setUnits(long cUnits) Set the size of this index in units (as defined by the UnitCalculator).
String	toString() Returns a string representation of this SimpleMapIndex.
String	toString(boolean fVerbose) Returns a string representation of this SimpleMapIndex.
void	update(Map.Entry entry) Update this index in response to an update operation on a cache.
protected void	updateExcludedKeys(Map.Entry entry, boolean fExclude) Check the entry against the set of entries not included in the index and update the set if necessary.
protected void	updateInternal(Map.Entry entry) Update this index in response to an update operation on a cache.

Methods inherited from class com.tangosol.util.Base

azzert, azzert, azzert, azzertFailed, breakLines, breakLines, capitalize, checkNotEmpty, checkNotNull, checkRange, computeSafeWaitTime, decimalValue, dup, dup, ensureBigDecimal, ensureClassLoader, ensureRuntimeException, ensureRuntimeException, equals, equalsDeep, err, err, err, err, err, escape, formatDateTime, getCallerStackFrame, getCommonMonitor, getCommonMonitor, getCommonMonitor, getContextClassLoader, getContextClassLoader, getDeepMessage, getErr, getLastSafeTimeMillis, getLog, getMaxDecDigits, getMaxHexDigits, getOriginalException, getOut, getProcessRandom, getRandom, getRandomBinary, getRandomBinary, getRandomString, getSafeTimeMillis, getStackFrame, getStackFrames, getStackTrace, getStackTrace, getThreadFactory, getTimeZone, getUpTimeMillis, hashCode, hexValue, indentString, indentString, isDecimal, isHex, isLogEcho, isOctal, log, log, log, log, log, makeInteger, makeLong, makeThread, mod, mod, octalValue, out, out, out, out, out, pad, parseBandwidth, parseBandwidth, parseDelimitedString, parseHex, parseHex, parseMemorySize, parseMemorySize, parsePercentage, parseTime, parseTime, parseTimeNanos, parseTimeNanos, printStackTrace, randomize, randomize, randomize, randomize, read, read, read, read, read, read, read, replace, setErr, setLog, setLogEcho, setOut, sleep, toBandwidthString, toBandwidthString, toCharEscape, toCrc, toCrc, toCrc, toCrc, toCrc, toDecString, toDelimitedString, toDelimitedString, toDelimitedString, toDelimitedString, toHex, toHex, toHexDump, toHexEscape, toHexEscape, toHexEscape, toHexEscape, toHexString, toMemorySizeString, toMemorySizeString, toQuotedCharEscape, toQuotedStringEscape, toSqlString, toString, toString, toStringEscape, toUnicodeEscape, trace, trace, trace, trace, trace, trace, trace, trace, trace, truncateString, truncateString, wait

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

m_extractor

protected ValueExtractor m_extractor

ValueExtractor object that this MapIndex uses to extract an indexable property value from a [converted] value stored in the resource map.

m_comparator

protected Comparator m_comparator

Comparator used to sort the index. Used iff the Ordered flag is true. Null implies a natural order.

m_fOrdered

protected boolean m_fOrdered

Specifies whether or not this MapIndex orders the contents of the indexed information.

m_mapForward

protected Map m_mapForward

Map that contains the index values (forward index). The keys of the Map are the keys to the map being indexed and the values are the extracted values. This map is used by the IndexAwareComparators to avoid a conversion and value extraction steps.

m_mapInverse

protected Map m_mapInverse

Map that contains the index contents (inverse index). The keys of the Map are the return values from the ValueExtractor operating against the entries of the resource map, and for each key, the corresponding value stored in the Map is a Set of keys to the resource map.

m_fSplitCollection

protected boolean m_fSplitCollection

If a value extracted by the ValueExtractor is a Collection, this property specifies whether or not it should be treated as a Collection of contained attributes or indexed as a single composite attribute.

m_cUnits

protected volatile long m_cUnits

The size footprint of the index, in units (as defined by the UnitCalculator).

m_calculator

protected ConfigurableCacheMap.UnitCalculator m_calculator

UnitCalculator used to estimate the cost of a value.

m_ctx

protected BackingMapContext m_ctx

The context associated with this index.

m_ldtLogMissingIdx

protected long m_ldtLogMissingIdx

The time at which the most recent logging of "missing inverse index" messages started.

m_cLogMissingIdx

protected int m_cLogMissingIdx

The number of "missing inverse index" messages that have been logged.

m_setKeyExcluded

protected Set m_setKeyExcluded

A set of keys for the entries, which could not be included in the index.

m_fForwardIndex

protected boolean m_fForwardIndex

Specifies whether or not this MapIndex supports a forward index.

m_fImmutableValues

protected boolean m_fImmutableValues

Specifies whether or not the index is based on the immutable values (e.g. keys).

Constructor Detail

SimpleMapIndex

public SimpleMapIndex(ValueExtractor extractor,
                      boolean fOrdered,
                      Comparator comparator,
                      BackingMapContext ctx)

Construct an index for the given map.

Parameters:

extractor - the ValueExtractor that is used to extract an indexed value from a resource map entry

fOrdered - true iff the contents of the indexed information should be ordered; false otherwise

comparator - the Comparator object which imposes an ordering on entries in the index map; or null if the entries' values natural ordering should be used

ctx - the context associated with the indexed cache

SimpleMapIndex

protected SimpleMapIndex(ValueExtractor extractor,
                         boolean fOrdered,
                         Comparator comparator,
                         boolean fInit,
                         BackingMapContext ctx)

Construct an index for the given map.

Parameters:

extractor - the ValueExtractor that is used to extract an indexed value from a resource map entry

fOrdered - true iff the contents of the indexed information should be ordered; false otherwise

comparator - the Comparator object which imposes an ordering on entries in the index map; or null if the entries' values natural ordering should be used

fInit - initialize the index if true

ctx - the context associated with the indexed cache

Method Detail

getValueExtractor

public ValueExtractor getValueExtractor()

Obtain the ValueExtractor object that the MapIndex uses to extract an indexable Object from a value stored in the indexed Map. This property is never null.

Specified by:

getValueExtractor in interface MapIndex

Returns:

a ValueExtractor object, never null

isOrdered

public boolean isOrdered()

Determine if the MapIndex orders the contents of the indexed information. To determine in which way the contents are ordered, get the Comparator from the index contents SortedMap object.

Specified by:

isOrdered in interface MapIndex

Returns:

true if the index contents are ordered, false otherwise

isPartial

public boolean isPartial()

Determine if indexed information for any entry in the indexed Map has been excluded from this index. This information is used for IndexAwareFilter implementations to determine the most optimal way to apply the index.

Note: Queries that use a partial index are allowed not to return entries that are not indexed even though they would match the corresponding filter were they evaluated during the full scan (if there were no index). However, it's not allowable for a query to return entries that do not match the corresponding filter, regardless of their presence in the index.

Specified by:

isPartial in interface MapIndex

Returns:

true if any entry of the indexed Map has been excluded from the index, false otherwise

getComparator

public Comparator getComparator()

Get the Comparator used to sort the index.

Specified by:

getComparator in interface MapIndex

Returns:

the comparator

getIndexContents

public Map getIndexContents()

Get the Map that contains the index contents.

The keys of the Map are the return values from the ValueExtractor operating against the indexed Map's values, and for each key, the corresponding value stored in the Map is a Set of keys to the indexed Map.

If the MapIndex is known to be ordered, then the returned Map object will be an instance of SortedMap. The SortedMap may or may not have a Comparator object associated with it; see SortedMap.comparator().

A client should assume that the returned Map object is read-only and must not attempt to modify it.

Specified by:

getIndexContents in interface MapIndex

Returns:

a Map (or a SortedMap) of the index contents

get

public Object get(Object oKey)

Using the index information if possible, get the value associated with the specified key. This is expected to be more efficient than using the ValueExtractor against an object containing the value, because the index should already have the necessary information at hand.

Specified by:

get in interface MapIndex

Parameters:

oKey - the key that specifies the object to extract the value from

Returns:

the value that would be extracted by this MapIndex's ValueExtractor from the object specified by the passed key; NO_VALUE if the index does not have the necessary information

insert

public void insert(Map.Entry entry)

Update this index in response to a insert operation on a cache.

Specified by:

insert in interface MapIndex

Parameters:

entry - the entry representing the object being inserted

update

public void update(Map.Entry entry)

Update this index in response to an update operation on a cache.

Specified by:

update in interface MapIndex

Parameters:

entry - the entry representing the object being updated

delete

public void delete(Map.Entry entry)

Update this index in response to a remove operation on a cache.

Specified by:

delete in interface MapIndex

Parameters:

entry - the entry representing the object being removed

isOptimizeMV

public boolean isOptimizeMV()

Specifies whether an attempt will be made to search the forward map for an existing reference that is "equal" to the specified mutli-value and use it instead (if available) to reduce the index memory footprint.

Returns:

true iff multi-value optimization is allowed

setOptimizeMV

public void setOptimizeMV(boolean fOptimizeMV)

For an indexed value that is a multi-value (Collection or array) this flag specifies whether an attempt should be made to search the forward map for an existing reference that is "equal" to the specified mutli-value and use it instead (if available) to reduce the index memory footprint.

Note, that even if this optimization is allowed, the full search could be quite expensive and our algorithm will always limit the number of cycles it spends on the search.

Parameters:

fOptimizeMV - the boolean value to set

getUnits

public long getUnits()

Retrieve the size of this index in units (as defined by the UnitCalculator).

Returns:

the index size

setUnits

protected void setUnits(long cUnits)

Set the size of this index in units (as defined by the UnitCalculator).

Parameters:

cUnits - new index size

getCalculator

public ConfigurableCacheMap.UnitCalculator getCalculator()

Return the UnitCalculator used to size this index's contents.

Returns:

the unit calculator

isForwardIndexSupported

public boolean isForwardIndexSupported()

Determine whether or not this SimpleMapIndex supports a forward index.

Returns:

true if this SimpleMapIndex supports a forward index; false otherwise

initialize

protected void initialize(boolean fForwardIndex)

Initialize the index's data structures.

Parameters:

fForwardIndex - specifies whether or not this index supports a forward map

getForwardEntry

protected Map.Entry getForwardEntry(Object oKey)

Get the forward index entry associated with the specified key.

Parameters:

oKey - the key

Returns:

the entry associated with the given key

addForwardEntry

protected void addForwardEntry(Object oKey,
                               Object oIxValueNew)

Add a new mapping to the forward index map.

Parameters:

oKey - the key to add to the mapping

oIxValueNew - the new value to add to the mapping

removeForwardEntry

protected void removeForwardEntry(Object oKey)

Remove the forward index entry for the specified key.

Parameters:

oKey - the key to remove the forward index entry for

extractNewValue

protected Object extractNewValue(Map.Entry entry)

Extract the "new" value from the specified entry.

Parameters:

entry - the entry to extract the "new" value from

Returns:

the extracted "new" value, or NO_VALUE if the extraction failed

extractOldValue

protected Object extractOldValue(MapTrigger.Entry entry)

Extract the "old" value from the specified entry.

Parameters:

entry - the entry to extract the "old" value from

Returns:

the extracted "old" value, or NO_VALUE if the extraction failed

ensureCollection

protected Collection ensureCollection(Object oValue)

Return a Collection representation of the specified value, which could be a Collection, Object[], scalar, or NO_VALUE.

Parameters:

oValue - the value

Returns:

a Collection representation of the specified value, or an empty Collection if NO_VALUE

instantiateForwardIndex

protected Map instantiateForwardIndex()

Instantiate the forward index.

Note: To optimize the memory footprint of the forward index, any subclasses of the SimpleMapIndex that override this method must also implement the getForwardEntry(Object) method accordingly.

Returns:

the forward index

instantiateInverseIndex

protected Map instantiateInverseIndex(boolean fOrdered,
                                      Comparator comparator)

Instantiate the inverse index.

Parameters:

fOrdered - true iff the contents of the indexed information should be ordered; false otherwise

comparator - the Comparator object which imposes an ordering on entries in the index map; or null if the entries' values natural ordering should be used

Returns:

the inverse index

insertInternal

protected void insertInternal(Map.Entry entry)

Update this index in response to a insert operation on a cache.

Parameters:

entry - the entry representing the object being inserted

updateInternal

protected void updateInternal(Map.Entry entry)

Update this index in response to an update operation on a cache.

Parameters:

entry - the entry representing the object being updated

deleteInternal

protected void deleteInternal(Map.Entry entry)

Update this index in response to a remove operation on a cache.

Parameters:

entry - the entry representing the object being removed

addInverseMapping

protected Object addInverseMapping(Object oIxValue,
                                   Object oKey)

Add a new mapping from the given indexed value to the given key in the inverse index.

Parameters:

oIxValue - the indexed value (serves as a key in the inverse index)

oKey - the key to insert into the inverse index

Returns:

an already existing reference that is "equal" to the specified value (if available)

addInverseMapping

protected Object addInverseMapping(Map mapIndex,
                                   Object oIxValue,
                                   Object oKey)

Add a new mapping from the given indexed value to the given key in the supplied index.

Parameters:

mapIndex - the index to which to add the mapping

oIxValue - the indexed value (serves as a key in the inverse index)

oKey - the key to insert into the inverse index

Returns:

an already existing reference that is "equal" to the specified value (if available)

addInverseCollectionMapping

protected Object addInverseCollectionMapping(Map mapIndex,
                                             Object oIxValue,
                                             Object oKey)

Add new mappings from the elements of the given value to the given key in the supplied index. The given value is expected to be either a Collection or an Object array.

Parameters:

mapIndex - the index to which to add the mapping

oIxValue - the indexed Collection value (each element serves as a key in the inverse index)

oKey - the key to insert into the inverse index

Returns:

an already existing reference that is "equal" to the specified value (if available)

removeInverseMapping

protected void removeInverseMapping(Object oIxValue,
                                    Object oKey,
                                    Collection colIgnore)

Remove the mapping from the given indexed value to the given key from the inverse index.

Parameters:

oIxValue - the indexed value, or NO_VALUE if unknown

oKey - the key

colIgnore - the Collection of values to ignore (exclude from removal), or null

removeInverseMapping

protected void removeInverseMapping(Object oIxValue,
                                    Object oKey)

Remove the mapping from the given indexed value to the given key from the inverse index.

Parameters:

oIxValue - the indexed value, or NO_VALUE if unknown

oKey - the key

removeInverseMapping

protected void removeInverseMapping(Map mapIndex,
                                    Object oIxValue,
                                    Object oKey)

Remove the mapping from the given indexed value to the given key from the supplied index.

Parameters:

mapIndex - the index from which to remove the mapping

oIxValue - the indexed value

oKey - the key

logMissingIdx

protected void logMissingIdx(Object oIxValue,
                             Object oKey)

Log messages for missing inverse index.

Parameters:

oIxValue - the indexed value

oKey - the key

collectRemoved

protected Set collectRemoved(Object oIxValueOld,
                             Object oIxValueNew)

Given that the old value is known to be a Collection or an array, collect all the enclosed elements that are not part of the new value.

Parameters:

oIxValueOld - the old value (must be a collection or an array)

oIxValueNew - the new value

Returns:

the set of values that are contained in the old collection or array, but not part of the new value

instantiateSet

protected Set instantiateSet()

Factory method used to create a new set containing the keys associated with a single value.

Returns:

a Set to keep the corresponding keys at

instantiateCalculator

protected ConfigurableCacheMap.UnitCalculator instantiateCalculator()

Factory method used to create a new calculator.

Returns:

a ConfigurableCacheMap.UnitCalculator

onMappingRemoved

protected void onMappingRemoved()

Decrease the size of the index by the size of an index map entry.

onMappingRemoved

protected void onMappingRemoved(Object oValue)

Decrease the size of the index by the estimated size of the specified removed value.

Parameters:

oValue - the value being removed from the index

onMappingAdded

protected void onMappingAdded()

Increase the size of the index by the size of an index map entry.

onMappingAdded

protected void onMappingAdded(Object oValue,
                              int cSize)

Increase the size of the index by the estimated size of the specified added value.

Parameters:

oValue - the value being added to the index

cSize - the current key set size indexed by the given value

updateExcludedKeys

protected void updateExcludedKeys(Map.Entry entry,
                                  boolean fExclude)

Check the entry against the set of entries not included in the index and update the set if necessary.

Parameters:

entry - the entry to be checked

fExclude - true iff the insert or update of the entry into the index caused an exception

isKeyExcluded

protected boolean isKeyExcluded(Object oKey)

Check if the entry with the given key is excluded from the index.

Parameters:

oKey - the key to test

Returns:

true if the key is in the list of keys currently excluded from the index, false if the entry with the key is in the index

toString

public String toString()

Returns a string representation of this SimpleMapIndex.

Overrides:

toString in class Object

Returns:

a String representation of this SimpleMapIndex

toString

public String toString(boolean fVerbose)

Returns a string representation of this SimpleMapIndex. If called in verbose mode, include the contents of the index (the inverse index). Otherwise, just print the number of entries in the index.

Parameters:

fVerbose - if true then print the content of the index otherwise print the number of entries

Returns:

a String representation of this SimpleMapIndex

equals

public boolean equals(Object o)

Compares the specified object with this index for equality. Returns true if the given object is also a SimpleMapIndex and the two represent the same index.

Overrides:

equals in class Object

Parameters:

o - object to be compared for equality with this MapIndex

Returns:

true if the specified object is equal to this index

hashCode

public int hashCode()

Returns the hash code value for this MapIndex.

Overrides:

hashCode in class Object

Returns:

the hash code value for this MapIndex