org.lenskit.util.keys

Class HashKeyIndex

java.lang.Object

org.lenskit.util.keys.HashKeyIndex

All Implemented Interfaces:

java.io.Serializable, KeyIndex

public final class HashKeyIndex
extends java.lang.Object
implements KeyIndex, java.io.Serializable

Mutable index mapping backed by a hash table. This mapping allows indexes to be obtained before all keys have been seen, making it very useful for incremental processing.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
HashKeyIndex() Construct a new empty indexer.

Method Summary

Modifier and Type	Method and Description
boolean	containsKey(long id) Query whether this index contains a particular key.
static HashKeyIndex	create()
static HashKeyIndex	create(LongList keys) Construct a new indexer.
static FrozenHashKeyIndex	createFrozen(LongList keys) Convenience method to create a frozen key index.
FrozenHashKeyIndex	frozenCopy() Make an immutable copy of this index mapping.
int	getIndex(long id) Get the index of a key.
long	getKey(int idx) Get the key for an index position.
LongList	getKeyList() Get the list of indexed keys.
int	getLowerBound() Get the lower bound of the index range for this index.
int	getUpperBound() Get the upper bound of the index range for this index.
int	internId(long key) Get an index for a key, generating a new one if necessary.
int	size() Get the size of this index.
int	tryGetIndex(long id) Try to get the index for an ID, returning a negative value if it does not exist.

Methods inherited from class java.lang.Object

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

Constructor Detail

HashKeyIndex

public HashKeyIndex()

Construct a new empty indexer. The first interned ID will have index 0.

Method Detail

create

public static HashKeyIndex create()

create

public static HashKeyIndex create(LongList keys)

Construct a new indexer. It maps each long key to its position in the list, and then be ready for more keys.

Parameters:

keys - The list of keys to store.

createFrozen

public static FrozenHashKeyIndex createFrozen(LongList keys)

Convenience method to create a frozen key index.

Parameters:

keys - The keys.

Returns:

A frozen index.

See Also:

FrozenHashKeyIndex.create(LongList)

getIndex

public int getIndex(long id)

Description copied from interface: KeyIndex

Get the index of a key.

Specified by:

getIndex in interface KeyIndex

Parameters:

id - The key to query.

Returns:

The key’s index.

containsKey

public boolean containsKey(long id)

Description copied from interface: KeyIndex

Query whether this index contains a particular key.

Specified by:

containsKey in interface KeyIndex

Parameters:

id - The key to look for.

Returns:

true if the index contains the key.

getKey

public long getKey(int idx)

Description copied from interface: KeyIndex

Get the key for an index position.

Specified by:

getKey in interface KeyIndex

Parameters:

idx - The index of the key to retrieve.

Returns:

The key for the given idx.

getKeyList

public LongList getKeyList()

Description copied from interface: KeyIndex

Get the list of indexed keys. This list is 0-indexed, so the key at position 0 in this list is at index KeyIndex.getLowerBound() in the key index.

Specified by:

getKeyList in interface KeyIndex

Returns:

The list of keys in the index. No key will appear twice.

tryGetIndex

public int tryGetIndex(long id)

Description copied from interface: KeyIndex

Try to get the index for an ID, returning a negative value if it does not exist. This method is like KeyIndex.getIndex(long), except it returns a negative value instead of throwing an exception if the id does not exist.

Specified by:

tryGetIndex in interface KeyIndex

Parameters:

id - The ID to look for.

Returns:

The index of the ID, or a negative value if it is not in the index.

size

public int size()

Description copied from interface: KeyIndex

Get the size of this index.

Specified by:

size in interface KeyIndex

Returns:

The number of indexed keys.

getLowerBound

public int getLowerBound()

Description copied from interface: KeyIndex

Get the lower bound of the index range for this index.

Specified by:

getLowerBound in interface KeyIndex

Returns:

The lower bound for the key index range.

getUpperBound

public int getUpperBound()

Description copied from interface: KeyIndex

Get the upper bound of the index range for this index.

Specified by:

getUpperBound in interface KeyIndex

Returns:

The upper bound for the key index range.

internId

public int internId(long key)

Get an index for a key, generating a new one if necessary.

Parameters:

key - The key.

Returns:

The index for key. If the key has already been added to the index, the old index is returned; otherwise, a new index is generated and returned.

frozenCopy

public FrozenHashKeyIndex frozenCopy()

Make an immutable copy of this index mapping.

Specified by:

frozenCopy in interface KeyIndex

Returns:

An immutable copy of the index mapping.