org.lenskit.util.keys

Class FrozenHashKeyIndex

java.lang.Object

org.lenskit.util.keys.FrozenHashKeyIndex

All Implemented Interfaces:

Serializable, KeyIndex

public final class FrozenHashKeyIndex
extends Object
implements KeyIndex, Serializable

Immutable key index backed by a hash table.

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
boolean	containsKey(long id) Query whether this index contains a particular key.
static FrozenHashKeyIndex	create(LongCollection keys) Create a new key index.
static FrozenHashKeyIndex	create(LongList keys) Construct a new key index.
FrozenHashKeyIndex	frozenCopy() Get a frozen copy of this key index.
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	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

Method Detail

create

public static FrozenHashKeyIndex create(LongList keys)

Construct a new key index. It maps each long key to its position in the list.

Parameters:

keys - The list of keys to store.

create

public static FrozenHashKeyIndex create(LongCollection keys)

Create a new key index.

Parameters:

keys - The keys.

Returns:

A key index containing the elements of keys.

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.

frozenCopy

public FrozenHashKeyIndex frozenCopy()

Description copied from interface: KeyIndex

Get a frozen copy of this key index. If the key index is mutable, then this method will return an immutable copy of it. If the key index is already immutable, it may just return itself without copying.

Specified by:

frozenCopy in interface KeyIndex

Returns:

An immutable key index with the same contents as this key index.