java.lang.Object
- com.googlecode.javaewah.datastructure.BitSet

All Implemented Interfaces:

WordArray, java.io.Externalizable, java.io.Serializable, java.lang.Cloneable, java.lang.Iterable<java.lang.Integer>
```
public class BitSet
extends java.lang.Object
implements java.lang.Cloneable, java.lang.Iterable<java.lang.Integer>, java.io.Externalizable, WordArray
```
This is an optimized version of Java's BitSet. In many cases, it can be used as a drop-in replacement.

It differs from the basic Java BitSet class in the following ways:
- You can iterate over set bits using a simpler syntax for(int bs: myBitset).
- You can compute the cardinality of an intersection and union without writing it out or modifying your BitSets (see methods such as andcardinality).
- You can recover wasted memory with trim().
- It does not implicitly expand: you have to explicitly call resize. This helps to keep memory usage in check.
- It supports memory-file mapping (see the ImmutableBitSet class).
- It supports faster and more efficient serialization functions (serialize and deserialize).
Since:

0.8.0

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type Field Description

(package private) long[] data

(package private) static long serialVersionUID

Constructor Summary

Constructors
Constructor Description

BitSet()

BitSet(int sizeInBits)
Construct a bitset with the specified number of bits (initially all false).

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`and(WordArray bs)`	Compute bitwise AND.
`int`	`andcardinality(WordArray bs)`	Compute cardinality of bitwise AND.
`void`	`andNot(WordArray bs)`	Compute bitwise AND NOT.
`int`	`andNotcardinality(WordArray bs)`	Compute cardinality of bitwise AND NOT.
`static BitSet`	`bitmapOf(int... setBits)`	Return a bitmap with the bit set to true at the given positions.
`int`	`cardinality()`	Compute the number of bits set to 1
`void`	`clear()`	Reset all bits to false.
`void`	`clear(int index)`	Set the bit to false.
`void`	`clear(int start, int end)`	Set the bits in the range of indexes to false.
`BitSet`	`clone()`
`void`	`deserialize(java.io.DataInput in)`	Deserialize.
`boolean`	`empty()`	Check whether a bitset contains a set bit.
`boolean`	`equals(java.lang.Object o)`
`void`	`flip(int i)`	Flip the bit.
`void`	`flip(int start, int end)`	Flip the bits in the range of indexes.
`boolean`	`get(int i)`	Get the value of the bit.
`int`	`getNumberOfWords()`	Get the total number of words contained in this data structure.
`long`	`getWord(int index)`	Get the word at the given index
`int`	`hashCode()`
`boolean`	`intersects(WordArray bs)`	Checks whether two bitsets intersect.
`IntIterator`	`intIterator()`	Iterate over the set bits
`java.util.Iterator<java.lang.Integer>`	`iterator()`
`int`	`nextSetBit(int i)`	Usage: for(int i=bs.nextSetBit(0); i>=0; i=bs.nextSetBit(i+1)) { operate on index i here }
`int`	`nextUnsetBit(int i)`	Usage: for(int i=bs.nextUnsetBit(0); i>=0; i=bs.nextUnsetBit(i+1)) { operate on index i here }
`void`	`or(WordArray bs)`	Compute bitwise OR.
`int`	`orcardinality(WordArray bs)`	Compute cardinality of bitwise OR.
`void`	`readExternal(java.io.ObjectInput in)`
`void`	`removeWord(int i)`	Remove a word.
`void`	`resize(int sizeInBits)`	Resize the bitset
`void`	`serialize(java.io.DataOutput out)`	Serialize.
`void`	`set(int i)`	Set to true.
`void`	`set(int i, boolean b)`	Set to some value.
`void`	`set(int start, int end)`	Set the bits in the range of indexes true.
`void`	`set(int start, int end, boolean v)`	Set the bits in the range of indexes to the specified Boolean value.
`int`	`size()`	Query the size
`java.lang.String`	`toString()`
`void`	`trim()`	Recovers wasted memory
`void`	`unset(int i)`	Set to false
`IntIterator`	`unsetIntIterator()`	Iterate over the unset bits
`void`	`writeExternal(java.io.ObjectOutput out)`
`void`	`xor(WordArray bs)`	Compute bitwise XOR.
`int`	`xorcardinality(WordArray bs)`	Compute cardinality of bitwise XOR.

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

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Field Detail
  - data
```
long[] data
```
  - serialVersionUID
```
static final long serialVersionUID
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - BitSet
```
public BitSet(int sizeInBits)
```
    Construct a bitset with the specified number of bits (initially all false). The number of bits is rounded up to the nearest multiple of 64.
    
    Parameters:
    
    sizeInBits - the size in bits
  - BitSet
```
public BitSet()
```
- Method Detail
  - and
```
public void and(WordArray bs)
```
    Compute bitwise AND.
    
    Parameters:
    
    bs - other bitset
  - andcardinality
```
public int andcardinality(WordArray bs)
```
    Compute cardinality of bitwise AND. The current bitmap is modified. Consider calling trim() to recover wasted memory afterward.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    cardinality
  - andNot
```
public void andNot(WordArray bs)
```
    Compute bitwise AND NOT. The current bitmap is modified. Consider calling trim() to recover wasted memory afterward.
    
    Parameters:
    
    bs - other bitset
  - andNotcardinality
```
public int andNotcardinality(WordArray bs)
```
    Compute cardinality of bitwise AND NOT.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    cardinality
  - cardinality
```
public int cardinality()
```
    Compute the number of bits set to 1
    
    Returns:
    
    the number of bits
  - clear
```
public void clear()
```
    Reset all bits to false. This might be wasteful: a better approach is to create a new empty bitmap.
  - clear
```
public void clear(int index)
```
    Set the bit to false. See unset(int)
    
    Parameters:
    
    index - location of the bit
  - clear
```
public void clear(int start,
                  int end)
```
    Set the bits in the range of indexes to false. This might throw an exception if size() is insufficient, consider calling resize().
    
    Parameters:
    
    start - location of the first bit to set to zero
    
    end - location of the last bit to set to zero (not included)
  - clone
```
public BitSet clone()
```
    Overrides:
    
    clone in class java.lang.Object
  - equals
```
public boolean equals(java.lang.Object o)
```
    Overrides:
    
    equals in class java.lang.Object
  - empty
```
public boolean empty()
```
    Check whether a bitset contains a set bit.
    
    Returns:
    
    true if no set bit is found
  - flip
```
public void flip(int i)
```
    Flip the bit. This might throw an exception if size() is insufficient, consider calling resize().
    
    Parameters:
    
    i - index of the bit
  - flip
```
public void flip(int start,
                 int end)
```
    Flip the bits in the range of indexes. This might throw an exception if size() is insufficient, consider calling resize().
    
    Parameters:
    
    start - location of the first bit
    
    end - location of the last bit (not included)
  - get
```
public boolean get(int i)
```
    Get the value of the bit. This might throw an exception if size() is insufficient, consider calling resize().
    
    Parameters:
    
    i - index
    
    Returns:
    
    value of the bit
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class java.lang.Object
  - intIterator
```
public IntIterator intIterator()
```
    Iterate over the set bits
    
    Returns:
    
    an iterator
  - iterator
```
public java.util.Iterator<java.lang.Integer> iterator()
```
    Specified by:
    
    iterator in interface java.lang.Iterable<java.lang.Integer>
  - intersects
```
public boolean intersects(WordArray bs)
```
    Checks whether two bitsets intersect.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    true if they have a non-empty intersection (result of AND)
  - nextSetBit
```
public int nextSetBit(int i)
```
    Usage: for(int i=bs.nextSetBit(0); i>=0; i=bs.nextSetBit(i+1)) { operate on index i here }
    
    Parameters:
    
    i - current set bit
    
    Returns:
    
    next set bit or -1
  - nextUnsetBit
```
public int nextUnsetBit(int i)
```
    Usage: for(int i=bs.nextUnsetBit(0); i>=0; i=bs.nextUnsetBit(i+1)) { operate on index i here }
    
    Parameters:
    
    i - current unset bit
    
    Returns:
    
    next unset bit or -1
  - or
```
public void or(WordArray bs)
```
    Compute bitwise OR. The current bitmap is modified. Consider calling trim() to recover wasted memory afterward.
    
    Parameters:
    
    bs - other bitset
  - orcardinality
```
public int orcardinality(WordArray bs)
```
    Compute cardinality of bitwise OR. BitSets are not modified.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    cardinality
  - removeWord
```
public void removeWord(int i)
```
    Remove a word.
    
    Parameters:
    
    i - index of the word to be removed.
  - resize
```
public void resize(int sizeInBits)
```
    Resize the bitset
    
    Parameters:
    
    sizeInBits - new number of bits
  - set
```
public void set(int i)
```
    Set to true. This might throw an exception if size() is insufficient, consider calling resize().
    
    Parameters:
    
    i - index of the bit
  - set
```
public void set(int i,
                boolean b)
```
    Set to some value. This might throw an exception if size() is insufficient, consider calling resize().
    
    Parameters:
    
    i - index
    
    b - value of the bit
  - set
```
public void set(int start,
                int end)
```
    Set the bits in the range of indexes true. This might throw an exception if size() is insufficient, consider calling resize().
    
    Parameters:
    
    start - location of the first bit
    
    end - location of the last bit (not included)
  - set
```
public void set(int start,
                int end,
                boolean v)
```
    Set the bits in the range of indexes to the specified Boolean value. This might throw an exception if size() is insufficient, consider calling resize().
    
    Parameters:
    
    start - location of the first bit
    
    end - location of the last bit (not included)
    
    v - Boolean value
  - size
```
public int size()
```
    Query the size
    
    Returns:
    
    the size in bits.
  - trim
```
public void trim()
```
    Recovers wasted memory
  - unset
```
public void unset(int i)
```
    Set to false
    
    Parameters:
    
    i - index of the bit
  - unsetIntIterator
```
public IntIterator unsetIntIterator()
```
    Iterate over the unset bits
    
    Returns:
    
    an iterator
  - writeExternal
```
public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException
```
    Specified by:
    
    writeExternal in interface java.io.Externalizable
    
    Throws:
    
    java.io.IOException
  - readExternal
```
public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException
```
    Specified by:
    
    readExternal in interface java.io.Externalizable
    
    Throws:
    
    java.io.IOException
    
    java.lang.ClassNotFoundException
  - serialize
```
public void serialize(java.io.DataOutput out)
               throws java.io.IOException
```
    Serialize. The current bitmap is not modified.
    
    Parameters:
    
    out - the DataOutput stream
    
    Throws:
    
    java.io.IOException - Signals that an I/O exception has occurred.
  - deserialize
```
public void deserialize(java.io.DataInput in)
                 throws java.io.IOException
```
    Deserialize.
    
    Parameters:
    
    in - the DataInput stream
    
    Throws:
    
    java.io.IOException - Signals that an I/O exception has occurred.
  - xor
```
public void xor(WordArray bs)
```
    Compute bitwise XOR. The current bitmap is modified. Consider calling trim() to recover wasted memory afterward.
    
    Parameters:
    
    bs - other bitset
  - xorcardinality
```
public int xorcardinality(WordArray bs)
```
    Compute cardinality of bitwise XOR. BitSets are not modified.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    cardinality
  - getNumberOfWords
```
public int getNumberOfWords()
```
    Description copied from interface: WordArray
    
    Get the total number of words contained in this data structure.
    
    Specified by:
    
    getNumberOfWords in interface WordArray
    
    Returns:
    
    the number
  - getWord
```
public long getWord(int index)
```
    Description copied from interface: WordArray
    
    Get the word at the given index
    
    Specified by:
    
    getWord in interface WordArray
    
    Parameters:
    
    index - the index
    
    Returns:
    
    the word
  - bitmapOf
```
public static BitSet bitmapOf(int... setBits)
```
    Return a bitmap with the bit set to true at the given positions. (This is a convenience method.)
    
    Parameters:
    
    setBits - list of set bit positions
    
    Returns:
    
    the bitmap
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object

Modifier and Type	Field	Description
`(package private) long[]`	`data`
`(package private) static long`	`serialVersionUID`

Constructor	Description
`BitSet()`
`BitSet(int sizeInBits)`	Construct a bitset with the specified number of bits (initially all false).

Class BitSet

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Field Detail

data

serialVersionUID

Constructor Detail

BitSet

BitSet

Method Detail

and

andcardinality

andNot

andNotcardinality

cardinality

clear

clear

clear

clone

equals

empty

flip

flip

get

hashCode

intIterator

iterator

intersects

nextSetBit

nextUnsetBit

or

orcardinality

removeWord

resize

set

set

set

set

size

trim

unset

unsetIntIterator

writeExternal

readExternal

serialize

deserialize

xor

xorcardinality

getNumberOfWords

getWord

bitmapOf

toString