BitSet (JavaEWAH 0.9.0 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().
Since:

0.8.0

Author:

Daniel Lemire

See Also:

Serialized Form

Constructor Summary

Constructors
Constructor and Description

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

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

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`and(BitSet bs)` Compute bitwise AND.
`int`	`andcardinality(BitSet bs)` Compute cardinality of bitwise AND.
`void`	`andNot(BitSet bs)` Compute bitwise AND NOT.
`int`	`andNotcardinality(BitSet bs)` Compute cardinality of bitwise AND NOT.
`int`	`cardinality()` Compute the number of bits set to 1
`void`	`clear()` Reset all bits to false.
`BitSet`	`clone()`
`boolean`	`empty()` Check whether a bitset contains a set bit.
`boolean`	`equals(Object o)`
`boolean`	`get(int i)`
`int`	`hashCode()`
`boolean`	`intersects(BitSet 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(BitSet bs)` Compute bitwise OR.
`int`	`orcardinality(BitSet bs)` Compute cardinality of bitwise OR.
`void`	`readExternal(ObjectInput in)`
`void`	`resize(int sizeInBits)` Resize the bitset
`void`	`set(int i)` Set to true
`void`	`set(int i, boolean b)`
`int`	`size()` Query the size
`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(BitSet bs)` Compute bitwise XOR.
`int`	`xorcardinality(BitSet bs)` Compute cardinality of bitwise XOR.

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, toString, 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
- Method Detail
  - and
```
public void and(BitSet bs)
```
    Compute bitwise AND.
    
    Parameters:
    
    bs - other bitset
  - andcardinality
```
public int andcardinality(BitSet 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(BitSet 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(BitSet 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()
             throws CloneNotSupportedException
```
    Overrides:
    
    clone in class Object
    
    Throws:
    
    CloneNotSupportedException
  - 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)
```
    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(BitSet 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(BitSet 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(BitSet bs)
```
    Compute cardinality of bitwise OR. BitSets are not modified.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    cardinality
  - readExternal
```
public void readExternal(ObjectInput in)
                  throws IOException,
                         ClassNotFoundException
```
    Specified by:
    
    readExternal in interface Externalizable
    
    Throws:
    
    IOException
    
    ClassNotFoundException
  - resize
```
public void resize(int sizeInBits)
```
    Resize the bitset
    
    Parameters:
    
    sizeInBits - new number of bits
  - set
```
public void set(int i)
```
    Set to true
    
    Parameters:
    
    i - index of the bit
  - set
```
public void set(int i,
                boolean b)
```
    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
  - xor
```
public void xor(BitSet 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(BitSet bs)
```
    Compute cardinality of bitwise XOR. BitSets are not modified.
    
    Parameters:
    
    bs - other bitset
    
    Returns:
    
    cardinality

Class BitSet

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Constructor Detail

BitSet

Method Detail

and

andcardinality

andNot

andNotcardinality

cardinality

clear

clone

equals

empty

get

hashCode

intIterator

iterator

intersects

nextSetBit

nextUnsetBit

or

orcardinality

readExternal

resize

set

set

size

trim

unset

unsetIntIterator

writeExternal

xor

xorcardinality