BitSet (JavaEWAH 1.0.1 API)

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

All Implemented Interfaces:

Externalizable, Serializable, Cloneable, Iterable<Integer>
```
public class BitSet
extends Object
implements Cloneable, Iterable<Integer>, Externalizable
```
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

Author:

Daniel Lemire

See Also:

Serialized Form

Constructor Summary

Constructors
Constructor and Description

BitSet()

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

Constructors
Constructor and 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 and Description
`void`	`and(com.googlecode.javaewah.datastructure.WordArray bs)` Compute bitwise AND.
`int`	`andcardinality(com.googlecode.javaewah.datastructure.WordArray bs)` Compute cardinality of bitwise AND.
`void`	`andNot(com.googlecode.javaewah.datastructure.WordArray bs)` Compute bitwise AND NOT.
`int`	`andNotcardinality(com.googlecode.javaewah.datastructure.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.
`BitSet`	`clone()`
`void`	`deserialize(DataInput in)` Deserialize.
`boolean`	`empty()` Check whether a bitset contains a set bit.
`boolean`	`equals(Object o)`
`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(com.googlecode.javaewah.datastructure.WordArray bs)` Checks whether two bitsets intersect.
`IntIterator`	`intIterator()` Iterate over the set bits
`Iterator<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(com.googlecode.javaewah.datastructure.WordArray bs)` Compute bitwise OR.
`int`	`orcardinality(com.googlecode.javaewah.datastructure.WordArray bs)` Compute cardinality of bitwise OR.
`void`	`readExternal(ObjectInput in)`
`void`	`resize(int sizeInBits)` Resize the bitset
`void`	`serialize(DataOutput out)` Serialize.
`void`	`set(int i)` Set to true.
`void`	`set(int i, boolean b)` Set to some value.
`int`	`size()` Query the size
`String`	`toString()`
`void`	`trim()` Recovers wasted memory
`void`	`unset(int i)` Set to false
`IntIterator`	`unsetIntIterator()` Iterate over the unset bits
`void`	`writeExternal(ObjectOutput out)`
`void`	`xor(com.googlecode.javaewah.datastructure.WordArray bs)` Compute bitwise XOR.
`int`	`xorcardinality(com.googlecode.javaewah.datastructure.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

- 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(com.googlecode.javaewah.datastructure.WordArray bs)
```
    Compute bitwise AND.
    
    Parameters:
    
    bs - other bitset
  - andcardinality
```
public int andcardinality(com.googlecode.javaewah.datastructure.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(com.googlecode.javaewah.datastructure.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(com.googlecode.javaewah.datastructure.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.
  - clone
```
public BitSet clone()
```
    Overrides:
    
    clone in class Object
  - equals
```
public boolean equals(Object o)
```
    Overrides:
    
    equals in class Object
  - empty
```
public boolean empty()
```
    Check whether a bitset contains a set bit.
    
    Returns:
    
    true if no set bit is found
  - 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 Object
  - intIterator
```
public IntIterator intIterator()
```
    Iterate over the set bits
    
    Returns:
    
    an iterator
  - iterator
```
public Iterator<Integer> iterator()
```
    Specified by:
    
    iterator in interface Iterable<Integer>
  - intersects
```
public boolean intersects(com.googlecode.javaewah.datastructure.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(com.googlecode.javaewah.datastructure.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(com.googlecode.javaewah.datastructure.WordArray bs)
```
    Compute cardinality of bitwise OR. BitSets are not modified.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    cardinality
  - 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
  - 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(ObjectOutput out)
                   throws IOException
```
    Specified by:
    
    writeExternal in interface Externalizable
    
    Throws:
    
    IOException
  - readExternal
```
public void readExternal(ObjectInput in)
                  throws IOException,
                         ClassNotFoundException
```
    Specified by:
    
    readExternal in interface Externalizable
    
    Throws:
    
    IOException
    
    ClassNotFoundException
  - serialize
```
public void serialize(DataOutput out)
               throws IOException
```
    Serialize. The current bitmap is not modified.
    
    Parameters:
    
    out - the DataOutput stream
    
    Throws:
    
    IOException - Signals that an I/O exception has occurred.
  - deserialize
```
public void deserialize(DataInput in)
                 throws IOException
```
    Deserialize.
    
    Parameters:
    
    in - the DataInput stream
    
    Throws:
    
    IOException - Signals that an I/O exception has occurred.
  - xor
```
public void xor(com.googlecode.javaewah.datastructure.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(com.googlecode.javaewah.datastructure.WordArray bs)
```
    Compute cardinality of bitwise XOR. BitSets are not modified.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    cardinality
  - getNumberOfWords
```
public int getNumberOfWords()
```
    Get the total number of words contained in this data structure.
    
    Returns:
    
    the number
  - getWord
```
public long getWord(int index)
```
    Get the word at the given index
    
    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 String toString()
```
    Overrides:
    
    toString in class Object

Class BitSet

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Constructor Detail

BitSet

BitSet

Method Detail

and

andcardinality

andNot

andNotcardinality

cardinality

clear

clone

equals

empty

get

hashCode

intIterator

iterator

intersects

nextSetBit

nextUnsetBit

or

orcardinality

resize

set

set

size

trim

unset

unsetIntIterator

writeExternal

readExternal

serialize

deserialize

xor

xorcardinality

getNumberOfWords

getWord

bitmapOf

toString