Package mondrian.rolap

Interface BitKey

All Superinterfaces:

Comparable<BitKey>, Iterable<Integer>, Serializable

All Known Implementing Classes:

BitKey.AbstractBitKey, BitKey.Big, BitKey.Mid128, BitKey.Small

public interface BitKey
extends Serializable, Comparable<BitKey>, Iterable<Integer>

Represents a set of bits.

Unlike BitSet, the number of bits cannot be changed after the BitKey is created. This allows us to optimize.

If you have a collection of immutable objects, each of which has a unique positive number and you wish to do comparisons between subsets of those objects testing for equality, then encoding the subsets as BitKeys is very efficient.

There are two implementations that target groups of objects with maximum number less than 64 and less than 128; and there is one implements that is general for any positive number.

One caution: if the maximum number assigned to one of the objects is large, then this representation might be sparse and therefore not efficient.

Author:

Richard M. Emberson

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	BitKey.AbstractBitKey	Abstract implementation of BitKey.
static class	BitKey.Big	Implementation of BitKey with more than 64 bits.
static class	BitKey.Factory
static class	BitKey.Mid128	Implementation of BitKey good for sizes less than 128.
static class	BitKey.Small	Implementation of BitKey for bit counts less than 64.

Field Summary

Fields

Modifier and Type	Field	Description
static final byte[]	bitPositionTable
static final BitKey	EMPTY	The BitKey with no bits set.

Method Summary

Modifier and Type	Method	Description
BitKey	and(BitKey bitKey)	Returns the boolean AND of this bitkey and the given bitkey.
BitKey	andNot(BitKey bitKey)	Returns a BitKey containing all of the bits in this BitSet whose corresponding bit is NOT set in the specified BitSet.
int	cardinality()	Returns the number of bits set.
void	clear()	Sets all of the bits in this BitKey to false.
void	clear(int bitIndex)	Sets the bit specified by the index to false.
BitKey	copy()	Returns a copy of this BitKey.
BitKey	emptyCopy()	Returns an empty BitKey of the same type.
boolean	get(int bitIndex)	Returns the value of the bit with the specified index.
boolean	intersects(BitKey bitKey)	Returns whether this BitKey has any bits in common with a given BitKey.
boolean	isEmpty()	Returns true if this BitKey contains no bits that are set to true.
boolean	isSuperSetOf(BitKey bitKey)	Is every bit set in the parameter bitKey also set in this.
Iterator<Integer>	iterator()	An Iterator over the bit positions.
int	nextSetBit(int fromIndex)	Returns the index of the first bit that is set to true that occurs on or after the specified starting index.
BitKey	or(BitKey bitKey)	Or the parameter BitKey with this.
BitKey	orNot(BitKey bitKey)	XOr the parameter BitKey with this.
void	set(int bitIndex)	Sets the bit at the specified index to true.
void	set(int bitIndex, boolean value)	Sets the bit at the specified index to the specified value.
BitSet	toBitSet()	Returns a BitSet with the same contents as this BitKey.

Methods inherited from interface java.lang.Comparable

compareTo

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Field Details

EMPTY

static final BitKey EMPTY

The BitKey with no bits set.

bitPositionTable

static final byte[] bitPositionTable

Method Details

set

void set(int bitIndex,
 boolean value)

Sets the bit at the specified index to the specified value.

set

void set(int bitIndex)

Sets the bit at the specified index to true.

get

boolean get(int bitIndex)

Returns the value of the bit with the specified index. The value is true if the bit with the index bitIndex is currently set in this BitKey; otherwise, the result is false.

clear

void clear(int bitIndex)

Sets the bit specified by the index to false.

clear

void clear()

Sets all of the bits in this BitKey to false.

isSuperSetOf

boolean isSuperSetOf(BitKey bitKey)

Is every bit set in the parameter bitKey also set in this. If one switches this with the parameter bitKey one gets the equivalent of isSubSetOf.

Parameters:

bitKey - Bit key

or

BitKey or(BitKey bitKey)

Or the parameter BitKey with this.

Parameters:

bitKey - Bit key

orNot

BitKey orNot(BitKey bitKey)

XOr the parameter BitKey with this.

Parameters:

bitKey - Bit key

and

BitKey and(BitKey bitKey)

Returns the boolean AND of this bitkey and the given bitkey.

Parameters:

bitKey - Bit key

andNot

BitKey andNot(BitKey bitKey)

Returns a BitKey containing all of the bits in this BitSet whose corresponding bit is NOT set in the specified BitSet.

copy

BitKey copy()

Returns a copy of this BitKey.

Returns:

copy of BitKey

emptyCopy

BitKey emptyCopy()

Returns an empty BitKey of the same type. This is the same as calling copy() followed by clear().

Returns:

BitKey of same type

isEmpty

boolean isEmpty()

Returns true if this BitKey contains no bits that are set to true.

intersects

boolean intersects(BitKey bitKey)

Returns whether this BitKey has any bits in common with a given BitKey.

toBitSet

BitSet toBitSet()

Returns a BitSet with the same contents as this BitKey.

iterator

Iterator<Integer> iterator()

An Iterator over the bit positions. For example, if the BitKey had positions 3 and 4 set, then the Iterator would return the values 3 and then 4. The bit positions returned by the iterator are in the order, from smallest to largest, as they are set in the BitKey.

Specified by:

iterator in interface Iterable<Integer>

nextSetBit

int nextSetBit(int fromIndex)

Returns the index of the first bit that is set to true that occurs on or after the specified starting index. If no such bit exists then -1 is returned. To iterate over the true bits in a BitKey, use the following loop:

 for (int i = bk.nextSetBit(0); i >= 0; i = bk.nextSetBit(i + 1)) {
     // operate on index i here
 }

Parameters:

fromIndex - the index to start checking from (inclusive)

Returns:

the index of the next set bit

Throws:

IndexOutOfBoundsException - if the specified index is negative

cardinality

int cardinality()

Returns the number of bits set.

Returns:

Number of bits set