java.lang.Object
- org.apache.lucene.util.BitSet
- - org.apache.lucene.util.FixedBitSet

All Implemented Interfaces:

Accountable, Bits
```
public final class FixedBitSet
extends BitSet
```
BitSet of fixed length (numBits), backed by accessible (getBits()) long[], accessed with an int index, implementing Bits and DocIdSet. If you need to manage more than 2.1B bits, use LongBitSet.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary
- Nested classes/interfaces inherited from interface org.apache.lucene.util.Bits
  Bits.MatchAllBits, Bits.MatchNoBits

Field Summary
- Fields inherited from interface org.apache.lucene.util.Accountable
  NULL_ACCOUNTABLE
- Fields inherited from interface org.apache.lucene.util.Bits
  EMPTY_ARRAY

Constructor Summary

Constructors
Constructor	Description
`FixedBitSet(int numBits)`	Creates a new LongBitSet.
`FixedBitSet(long[] storedBits, int numBits)`	Creates a new LongBitSet using the provided long[] array as backing store.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`and(FixedBitSet other)`	this = this AND other
`void`	`andNot(DocIdSetIterator iter)`
`void`	`andNot(FixedBitSet other)`	this = this AND NOT other
`static long`	`andNotCount(FixedBitSet a, FixedBitSet b)`	Returns the popcount or cardinality of "a and not b" or "intersection(a, not(b))".
`int`	`approximateCardinality()`	Return an approximation of the cardinality of this set.
`Bits`	`asReadOnlyBits()`	Convert this instance to read-only `Bits`.
`static int`	`bits2words(int numBits)`	returns the number of 64 bit words it would take to hold numBits
`int`	`cardinality()`	Returns number of set bits.
`void`	`clear()`	Clear all the bits of the set.
`void`	`clear(int index)`	Clear the bit at `i`.
`void`	`clear(int startIndex, int endIndex)`	Clears a range of bits.
`FixedBitSet`	`clone()`
`static FixedBitSet`	`copyOf(Bits bits)`	Make a copy of the given bits.
`static FixedBitSet`	`ensureCapacity(FixedBitSet bits, int numBits)`	If the given `FixedBitSet` is large enough to hold `numBits+1`, returns the given bits, otherwise returns a new `FixedBitSet` which can hold the requested number of bits.
`boolean`	`equals(Object o)`
`void`	`flip(int index)`	Flip the bit at the provided index.
`void`	`flip(int startIndex, int endIndex)`	Flips a range of bits
`boolean`	`get(int index)`	Returns the value of the bit with the specified `index`.
`boolean`	`getAndClear(int index)`
`boolean`	`getAndSet(int index)`	Set the bit at `i`, returning `true` if it was previously set.
`long[]`	`getBits()`	Expert.
`int`	`hashCode()`
`static long`	`intersectionCount(FixedBitSet a, FixedBitSet b)`	Returns the popcount or cardinality of the intersection of the two sets.
`boolean`	`intersects(FixedBitSet other)`	returns true if the sets have any elements in common
`int`	`length()`	Returns the number of bits in this set
`int`	`nextSetBit(int index)`	Returns the index of the first set bit starting at the index specified.
`void`	`or(DocIdSetIterator iter)`	Does in-place OR of the bits provided by the iterator.
`void`	`or(FixedBitSet other)`	this = this OR other
`int`	`prevSetBit(int index)`	Returns the index of the last set bit before or on the index specified.
`long`	`ramBytesUsed()`	Return the memory usage of this object in bytes.
`boolean`	`scanIsEmpty()`	Scans the backing store to check if all bits are clear.
`void`	`set(int index)`	Set the bit at `i`.
`void`	`set(int startIndex, int endIndex)`	Sets a range of bits
`static long`	`unionCount(FixedBitSet a, FixedBitSet b)`	Returns the popcount or cardinality of the union of the two sets.
`void`	`xor(DocIdSetIterator iter)`	Does in-place XOR of the bits provided by the iterator.
`void`	`xor(FixedBitSet other)`	this = this XOR other

Methods inherited from class org.apache.lucene.util.BitSet
checkUnpositioned, of

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.lucene.util.Accountable
getChildResources

- Constructor Detail
  - FixedBitSet
```
public FixedBitSet(int numBits)
```
    Creates a new LongBitSet. The internally allocated long array will be exactly the size needed to accommodate the numBits specified.
    
    Parameters:
    
    numBits - the number of bits needed
  - FixedBitSet
```
public FixedBitSet(long[] storedBits,
                   int numBits)
```
    Creates a new LongBitSet using the provided long[] array as backing store. The storedBits array must be large enough to accommodate the numBits specified, but may be larger. In that case the 'extra' or 'ghost' bits must be clear (or they may provoke spurious side-effects)
    
    Parameters:
    
    storedBits - the array to use as backing store
    
    numBits - the number of bits actually needed
- Method Detail
  - ensureCapacity
```
public static FixedBitSet ensureCapacity(FixedBitSet bits,
                                         int numBits)
```
    If the given FixedBitSet is large enough to hold numBits+1, returns the given bits, otherwise returns a new FixedBitSet which can hold the requested number of bits.
    NOTE: the returned bitset reuses the underlying long[] of the given bits if possible. Also, calling length() on the returned bits may return a value greater than numBits.
  - bits2words
```
public static int bits2words(int numBits)
```
    returns the number of 64 bit words it would take to hold numBits
  - intersectionCount
```
public static long intersectionCount(FixedBitSet a,
                                     FixedBitSet b)
```
    Returns the popcount or cardinality of the intersection of the two sets. Neither set is modified.
  - unionCount
```
public static long unionCount(FixedBitSet a,
                              FixedBitSet b)
```
    Returns the popcount or cardinality of the union of the two sets. Neither set is modified.
  - andNotCount
```
public static long andNotCount(FixedBitSet a,
                               FixedBitSet b)
```
    Returns the popcount or cardinality of "a and not b" or "intersection(a, not(b))". Neither set is modified.
  - clear
```
public void clear()
```
    Description copied from class: BitSet
    
    Clear all the bits of the set.
    Depending on the implementation, this may be significantly faster than clear(0, length).
    
    Overrides:
    
    clear in class BitSet
  - length
```
public int length()
```
    Description copied from interface: Bits
    
    Returns the number of bits in this set
  - ramBytesUsed
```
public long ramBytesUsed()
```
    Description copied from interface: Accountable
    
    Return the memory usage of this object in bytes. Negative values are illegal.
  - getBits
```
public long[] getBits()
```
    Expert.
  - cardinality
```
public int cardinality()
```
    Returns number of set bits. NOTE: this visits every long in the backing bits array, and the result is not internally cached!
    
    Specified by:
    
    cardinality in class BitSet
  - approximateCardinality
```
public int approximateCardinality()
```
    Description copied from class: BitSet
    
    Return an approximation of the cardinality of this set. Some implementations may trade accuracy for speed if they have the ability to estimate the cardinality of the set without iterating over all the data. The default implementation returns BitSet.cardinality().
    
    Specified by:
    
    approximateCardinality in class BitSet
  - get
```
public boolean get(int index)
```
    Description copied from interface: Bits
    
    Returns the value of the bit with the specified index.
    
    Parameters:
    
    index - index, should be non-negative and < Bits.length(). The result of passing negative or out of bounds values is undefined by this interface, just don't do it!
    
    Returns:
    
    true if the bit is set, false otherwise.
  - set
```
public void set(int index)
```
    Description copied from class: BitSet
    
    Set the bit at i.
    
    Specified by:
    
    set in class BitSet
  - getAndSet
```
public boolean getAndSet(int index)
```
    Description copied from class: BitSet
    
    Set the bit at i, returning true if it was previously set.
    
    Specified by:
    
    getAndSet in class BitSet
  - clear
```
public void clear(int index)
```
    Description copied from class: BitSet
    
    Clear the bit at i.
    
    Specified by:
    
    clear in class BitSet
  - getAndClear
```
public boolean getAndClear(int index)
```
  - nextSetBit
```
public int nextSetBit(int index)
```
    Description copied from class: BitSet
    
    Returns the index of the first set bit starting at the index specified. DocIdSetIterator.NO_MORE_DOCS is returned if there are no more set bits.
    
    Specified by:
    
    nextSetBit in class BitSet
  - prevSetBit
```
public int prevSetBit(int index)
```
    Description copied from class: BitSet
    
    Returns the index of the last set bit before or on the index specified. -1 is returned if there are no more set bits.
    
    Specified by:
    
    prevSetBit in class BitSet
  - or
```
public void or(DocIdSetIterator iter)
        throws IOException
```
    Description copied from class: BitSet
    
    Does in-place OR of the bits provided by the iterator. The state of the iterator after this operation terminates is undefined.
    
    Overrides:
    
    or in class BitSet
    
    Throws:
    
    IOException
  - or
```
public void or(FixedBitSet other)
```
    this = this OR other
  - xor
```
public void xor(FixedBitSet other)
```
    this = this XOR other
  - xor
```
public void xor(DocIdSetIterator iter)
         throws IOException
```
    Does in-place XOR of the bits provided by the iterator.
    
    Throws:
    
    IOException
  - intersects
```
public boolean intersects(FixedBitSet other)
```
    returns true if the sets have any elements in common
  - and
```
public void and(FixedBitSet other)
```
    this = this AND other
  - andNot
```
public void andNot(DocIdSetIterator iter)
            throws IOException
```
    Throws:
    
    IOException
  - andNot
```
public void andNot(FixedBitSet other)
```
    this = this AND NOT other
  - scanIsEmpty
```
public boolean scanIsEmpty()
```
    Scans the backing store to check if all bits are clear. The method is deliberately not called "isEmpty" to emphasize it is not low cost (as isEmpty usually is).
    
    Returns:
    
    true if all bits are clear.
  - flip
```
public void flip(int startIndex,
                 int endIndex)
```
    Flips a range of bits
    
    Parameters:
    
    startIndex - lower index
    
    endIndex - one-past the last bit to flip
  - flip
```
public void flip(int index)
```
    Flip the bit at the provided index.
  - set
```
public void set(int startIndex,
                int endIndex)
```
    Sets a range of bits
    
    Parameters:
    
    startIndex - lower index
    
    endIndex - one-past the last bit to set
  - clear
```
public void clear(int startIndex,
                  int endIndex)
```
    Description copied from class: BitSet
    
    Clears a range of bits.
    
    Specified by:
    
    clear in class BitSet
    
    Parameters:
    
    startIndex - lower index
    
    endIndex - one-past the last bit to clear
  - clone
```
public FixedBitSet clone()
```
    Overrides:
    
    clone in class Object
  - equals
```
public boolean equals(Object o)
```
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
  - copyOf
```
public static FixedBitSet copyOf(Bits bits)
```
    Make a copy of the given bits.
  - asReadOnlyBits
```
public Bits asReadOnlyBits()
```
    Convert this instance to read-only Bits. This is useful in the case that this FixedBitSet is returned as a Bits instance, to make sure that consumers may not get write access back by casting to a FixedBitSet. NOTE: Changes to this FixedBitSet will be reflected on the returned Bits.

Class FixedBitSet

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.lucene.util.Bits

Field Summary

Fields inherited from interface org.apache.lucene.util.Accountable

Fields inherited from interface org.apache.lucene.util.Bits

Constructor Summary

Method Summary

Methods inherited from class org.apache.lucene.util.BitSet

Methods inherited from class java.lang.Object

Methods inherited from interface org.apache.lucene.util.Accountable

Constructor Detail

FixedBitSet

FixedBitSet

Method Detail

ensureCapacity

bits2words

intersectionCount

unionCount

andNotCount

clear

length

ramBytesUsed

getBits

cardinality

approximateCardinality

get

set

getAndSet

clear

getAndClear

nextSetBit

prevSetBit

or

or

xor

xor

intersects

and

andNot

andNot

scanIsEmpty

flip

flip

set

clear

clone

equals

hashCode

copyOf

asReadOnlyBits