org.lenskit.util.keys

Interface KeyIndex

All Known Implementing Classes:

FrozenHashKeyIndex, HashKeyIndex, SortedKeyIndex

public interface KeyIndex

Bidirectional mapping between long keys and a contiguous range of integer indexes.

Method Summary

Modifier and Type	Method and Description
boolean	containsKey(long key) Query whether this index contains a particular key.
KeyIndex	frozenCopy() Get a frozen copy of this key index.
int	getIndex(long key) 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.

Method Detail

getIndex

int getIndex(long key)

Get the index of a key.

Parameters:

key - The key to query.

Returns:

The key’s index.

Throws:

java.lang.IllegalArgumentException - if key is not in the index.

containsKey

boolean containsKey(long key)

Query whether this index contains a particular key.

Parameters:

key - The key to look for.

Returns:

true if the index contains the key.

getKey

long getKey(int idx)

Get the key for an index position.

Parameters:

idx - The index of the key to retrieve.

Returns:

The key for the given idx.

Throws:

java.lang.IndexOutOfBoundsException - if idx is not a valid index.

tryGetIndex

int tryGetIndex(long id)

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

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

int size()

Get the size of this index.

Returns:

The number of indexed keys.

getLowerBound

int getLowerBound()

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

Returns:

The lower bound for the key index range.

getUpperBound

int getUpperBound()

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

Returns:

The upper bound for the key index range.

getKeyList

LongList getKeyList()

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

Returns:

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

frozenCopy

KeyIndex frozenCopy()

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.

Returns:

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