java.lang.Object
- org.apache.lucene.search.DocIdSet
- - org.apache.lucene.util.FixedBitSet

All Implemented Interfaces:

Bits
```
public final class FixedBitSet
extends DocIdSet
implements Bits
```
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.

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class FixedBitSet.FixedBitSetIterator
A DocIdSetIterator which iterates over set bits in a FixedBitSet.
- 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.Bits
  EMPTY_ARRAY

Constructor Summary

Constructors
Constructor Description

FixedBitSet(int numBits)

FixedBitSet(long[] storedBits, int numBits)

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`and(DocIdSetIterator iter)`	Does in-place AND of the bits provided by the iterator.
`void`	`and(FixedBitSet other)`	this = this AND other
`void`	`andNot(DocIdSetIterator iter)`	Does in-place AND NOT of the bits provided by the iterator.
`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))".
`Bits`	`bits()`	Optionally provides a `Bits` interface for random access to matching documents.
`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(int index)`
`void`	`clear(int startIndex, int endIndex)`	Clears a range of bits.
`FixedBitSet`	`clone()`
`static FixedBitSet`	`ensureCapacity(FixedBitSet bits, int numBits)`	If the given `FixedBitSet` is large enough to hold `numBits`, returns the given bits, otherwise returns a new `FixedBitSet` which can hold the requested number of bits.
`boolean`	`equals(java.lang.Object o)`	returns true if both sets have the same bits set
`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)`
`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
`boolean`	`isCacheable()`	This DocIdSet implementation is cacheable.
`DocIdSetIterator`	`iterator()`	Provides a `DocIdSetIterator` to access the set.
`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.
`void`	`set(int index)`
`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 java.lang.Object
getClass, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - FixedBitSet
```
public FixedBitSet(int numBits)
```
  - FixedBitSet
```
public FixedBitSet(long[] storedBits,
                   int numBits)
```
- Method Detail
  - ensureCapacity
```
public static FixedBitSet ensureCapacity(FixedBitSet bits,
                                         int numBits)
```
    If the given FixedBitSet is large enough to hold numBits, 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.
  - iterator
```
public DocIdSetIterator iterator()
```
    Description copied from class: DocIdSet
    
    Provides a DocIdSetIterator to access the set. This implementation can return null if there are no docs that match.
    
    Specified by:
    
    iterator in class DocIdSet
  - bits
```
public Bits bits()
```
    Description copied from class: DocIdSet
    
    Optionally provides a Bits interface for random access to matching documents.
    
    Overrides:
    
    bits in class DocIdSet
    
    Returns:
    
    null, if this DocIdSet does not support random access. In contrast to DocIdSet.iterator(), a return value of null does not imply that no documents match the filter! The default implementation does not provide random access, so you only need to implement this method if your DocIdSet can guarantee random access to every docid in O(1) time without external disk access (as Bits interface cannot throw IOException). This is generally true for bit sets like FixedBitSet, which return itself if they are used as DocIdSet.
  - length
```
public int length()
```
    Description copied from interface: Bits
    
    Returns the number of bits in this set
    
    Specified by:
    
    length in interface Bits
  - isCacheable
```
public boolean isCacheable()
```
    This DocIdSet implementation is cacheable.
    
    Overrides:
    
    isCacheable in class DocIdSet
  - 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!
  - get
```
public boolean get(int index)
```
    Description copied from interface: Bits
    
    Returns the value of the bit with the specified index.
    
    Specified by:
    
    get in interface Bits
    
    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)
```
  - getAndSet
```
public boolean getAndSet(int index)
```
  - clear
```
public void clear(int index)
```
  - getAndClear
```
public boolean getAndClear(int index)
```
  - nextSetBit
```
public int nextSetBit(int index)
```
    Returns the index of the first set bit starting at the index specified. -1 is returned if there are no more set bits.
  - prevSetBit
```
public int prevSetBit(int index)
```
    Returns the index of the last set bit before or on the index specified. -1 is returned if there are no more set bits.
  - or
```
public void or(DocIdSetIterator iter)
        throws java.io.IOException
```
    Does in-place OR of the bits provided by the iterator.
    
    Throws:
    
    java.io.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 java.io.IOException
```
    Does in-place XOR of the bits provided by the iterator.
    
    Throws:
    
    java.io.IOException
  - and
```
public void and(DocIdSetIterator iter)
         throws java.io.IOException
```
    Does in-place AND of the bits provided by the iterator.
    
    Throws:
    
    java.io.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 java.io.IOException
```
    Does in-place AND NOT of the bits provided by the iterator.
    
    Throws:
    
    java.io.IOException
  - andNot
```
public void andNot(FixedBitSet other)
```
    this = this AND NOT other
  - 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
  - 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)
```
    Clears a range of bits.
    
    Parameters:
    
    startIndex - lower index
    
    endIndex - one-past the last bit to clear
  - clone
```
public FixedBitSet clone()
```
  - equals
```
public boolean equals(java.lang.Object o)
```
    returns true if both sets have the same bits set
    
    Overrides:
    
    equals in class java.lang.Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class java.lang.Object

Constructor	Description
`FixedBitSet(int numBits)`
`FixedBitSet(long[] storedBits, int numBits)`

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.Bits

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

FixedBitSet

FixedBitSet

Method Detail

ensureCapacity

bits2words

intersectionCount

unionCount

andNotCount

iterator

bits

length

isCacheable

getBits

cardinality

get

set

getAndSet

clear

getAndClear

nextSetBit

prevSetBit

or

or

xor

xor

and

intersects

and

andNot

andNot

flip

set

clear

clone

equals

hashCode