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`java.lang.Object`

`java.util.BitSet`

**Implemented Interfaces:**- Cloneable, Serializable

This class can be thought of in two ways. You can see it as a
vector of bits or as a set of non-negative integers. The name

`BitSet`

is a bit misleading.
It is implemented by a bit vector, but its equally possible to see
it as set of non-negative integer; each integer in the set is
represented by a set bit at the corresponding index. The size of
this structure is determined by the highest integer in the set.
You can union, intersect and build (symmetric) remainders, by
invoking the logical operations and, or, andNot, resp. xor.
This implementation is NOT synchronized against concurrent access from
multiple threads. Specifically, if one thread is reading from a bitset
while another thread is simultaneously modifying it, the results are
undefined.
**See Also:**- Serialized Form

## Constructor Summary

`BitSet()`

- Create a new empty bit set.

`BitSet(int nbits)`

- Create a new empty bit set, with a given size.

## Method Summary

`void`

`void`

`int`

`cardinality()`

- Returns the number of bits set to true.

`void`

`clear()`

- Sets all bits in the set to false.

`void`

`clear(int pos)`

- Removes the integer
`pos`

from this set.

`void`

`clear(int from, int to)`

- Sets the bits between from (inclusive) and to (exclusive) to false.

`Object`

`clone()`

- Create a clone of this bit set, that is an instance of the same class and contains the same elements.

`boolean`

`void`

`flip(int index)`

- Sets the bit at the index to the opposite value.

`void`

`flip(int from, int to)`

- Sets a range of bits to the opposite value.

`boolean`

`get(int pos)`

- Returns true if the integer
`bitIndex`

is in this bit set, otherwise false.

`BitSet`

`get(int from, int to)`

- Returns a new
`BitSet`

composed of a range of bits from this one.

`int`

`hashCode()`

- Returns a hash code value for this bit set.

`boolean`

`intersects(BitSet set)`

- Returns true if the specified BitSet and this one share at least one common true bit.

`boolean`

`isEmpty()`

- Returns true if this set contains no true bits.

`int`

`length()`

- Returns the logical number of bits actually used by this bit set.

`int`

`nextClearBit(int from)`

- Returns the index of the next false bit, from the specified bit (inclusive).

`int`

`nextSetBit(int from)`

- Returns the index of the next true bit, from the specified bit (inclusive).

`void`

`void`

`set(int pos)`

- Add the integer
`bitIndex`

to this set.

`void`

`set(int index, boolean value)`

- Sets the bit at the given index to the specified value.

`void`

`set(int from, int to)`

- Sets the bits between from (inclusive) and to (exclusive) to true.

`void`

`set(int from, int to, boolean value)`

- Sets the bits between from (inclusive) and to (exclusive) to the specified value.

`int`

`size()`

- Returns the number of bits actually used by this bit set.

`String`

`toString()`

- Returns the string representation of this bit set.

`void`

### Methods inherited from class java.lang.Object

`clone`

,`equals`

,`extends Object> getClass`

,`finalize`

,`hashCode`

,`notify`

,`notifyAll`

,`toString`

,`wait`

,`wait`

,`wait`

public BitSet(int nbits)

Create a new empty bit set, with a given size. This constructor reserves enough space to represent the integers from`0`

to`nbits-1`

.

Parameters:`nbits`

- the initial size of the bit set

Throws:`NegativeArraySizeException`

- if nbits < 0

public void and(BitSet bs)

Performs the logical AND operation on this bit set and the given`set`

. This means it builds the intersection of the two sets. The result is stored into this bit set.

Parameters:`bs`

- the second bit set

Throws:`NullPointerException`

- if bs is null

public void andNot(BitSet bs)

Performs the logical AND operation on this bit set and the complement of the given`bs`

. This means it selects every element in the first set, that isn't in the second set. The result is stored into this bit set and is effectively the set difference of the two.

Parameters:`bs`

- the second bit set

Throws:`NullPointerException`

- if bs is null

Since:- 1.2

public int cardinality()

Returns the number of bits set to true.

Returns:- the number of true bits

Since:- 1.4

public void clear(int pos)

Removes the integer`pos`

from this set. That is the corresponding bit is cleared. If the index is not in the set, this method does nothing.

Parameters:`pos`

- a non-negative integer

Throws:`IndexOutOfBoundsException`

- if pos < 0

public void clear(int from, int to)

Sets the bits between from (inclusive) and to (exclusive) to false.

Parameters:`from`

- the start range (inclusive)`to`

- the end range (exclusive)

Throws:`IndexOutOfBoundsException`

- if from < 0 || to < 0 || from > to

Since:- 1.4

public Object clone()

Create a clone of this bit set, that is an instance of the same class and contains the same elements. But it doesn't change when this bit set changes.

Returns:- the clone of this object.

public boolean equals(Object obj)

Returns true if the`obj`

is a bit set that contains exactly the same elements as this bit set, otherwise false.

Parameters:`obj`

- the object to compare to

Returns:- true if obj equals this bit set

public void flip(int index)

Sets the bit at the index to the opposite value.

Parameters:`index`

- the index of the bit

Throws:`IndexOutOfBoundsException`

- if index is negative

Since:- 1.4

public void flip(int from, int to)

Sets a range of bits to the opposite value.

Parameters:`from`

- the low index (inclusive)`to`

- the high index (exclusive)

Throws:`IndexOutOfBoundsException`

- if from > to || from < 0 || to < 0

Since:- 1.4

public boolean get(int pos)

Returns true if the integer`bitIndex`

is in this bit set, otherwise false.

Parameters:`pos`

- a non-negative integer

Returns:- the value of the bit at the specified position

Throws:`IndexOutOfBoundsException`

- if the pos is negative

public BitSet get(int from, int to)

Returns a new`BitSet`

composed of a range of bits from this one.

Parameters:`from`

- the low index (inclusive)`to`

- the high index (exclusive)

Throws:`IndexOutOfBoundsException`

- if from > to || from < 0 || to < 0

Since:- 1.4

public int hashCode()

Returns a hash code value for this bit set. The hash code of two bit sets containing the same integers is identical. The algorithm used to compute it is as follows: Suppose the bits in the BitSet were to be stored in an array of long integers called`bits`

, in such a manner that bit`k`

is set in the BitSet (for non-negative values of`k`

) if and only if`((k/64) < bits.length) && ((bits[k/64] & (1L << (bit % 64))) != 0)`

Then the following definition of the hashCode method would be a correct implementation of the actual algorithm:public int hashCode() { long h = 1234; for (int i = bits.length-1; i >= 0; i--) { h ^= bits[i] * (i + 1); } return (int)((h >> 32) ^ h); }Note that the hash code values changes, if the set is changed.

Returns:- the hash code value for this bit set.

public boolean intersects(BitSet set)

Returns true if the specified BitSet and this one share at least one common true bit.

Parameters:`set`

- the set to check for intersection

Returns:- true if the sets intersect

Throws:`NullPointerException`

- if set is null

Since:- 1.4

public boolean isEmpty()

Returns true if this set contains no true bits.

Returns:- true if all bits are false

Since:- 1.4

public int length()

Returns the logical number of bits actually used by this bit set. It returns the index of the highest set bit plus one. Note that this method doesn't return the number of set bits.

Returns:- the index of the highest set bit plus one.

public int nextClearBit(int from)

Returns the index of the next false bit, from the specified bit (inclusive).

Parameters:`from`

- the start location

Returns:- the first false bit

Throws:`IndexOutOfBoundsException`

- if from is negative

Since:- 1.4

public int nextSetBit(int from)

Returns the index of the next true bit, from the specified bit (inclusive). If there is none, -1 is returned. You can iterate over all true bits with this loop:

for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i + 1)) { // operate on i here }

Parameters:`from`

- the start location

Returns:- the first true bit, or -1

Throws:`IndexOutOfBoundsException`

- if from is negative

Since:- 1.4

public void or(BitSet bs)

Performs the logical OR operation on this bit set and the given`set`

. This means it builds the union of the two sets. The result is stored into this bit set, which grows as necessary.

Parameters:`bs`

- the second bit set

Throws:`NullPointerException`

- if bs is null

public void set(int pos)

Add the integer`bitIndex`

to this set. That is the corresponding bit is set to true. If the index was already in the set, this method does nothing. The size of this structure is automatically increased as necessary.

Parameters:`pos`

- a non-negative integer.

Throws:`IndexOutOfBoundsException`

- if pos is negative

public void set(int index, boolean value)

Sets the bit at the given index to the specified value. The size of this structure is automatically increased as necessary.

Parameters:`index`

- the position to set`value`

- the value to set it to

Throws:`IndexOutOfBoundsException`

- if index is negative

Since:- 1.4

public void set(int from, int to)

Sets the bits between from (inclusive) and to (exclusive) to true.

Parameters:`from`

- the start range (inclusive)`to`

- the end range (exclusive)

Throws:`IndexOutOfBoundsException`

- if from < 0 || from > to || to < 0

Since:- 1.4

public void set(int from, int to, boolean value)

Sets the bits between from (inclusive) and to (exclusive) to the specified value.

Parameters:`from`

- the start range (inclusive)`to`

- the end range (exclusive)`value`

- the value to set it to

Throws:`IndexOutOfBoundsException`

- if from < 0 || from > to || to < 0

Since:- 1.4

public int size()

Returns the number of bits actually used by this bit set. Note that this method doesn't return the number of set bits, and that future requests for larger bits will make this automatically grow.

Returns:- the number of bits currently used.

public String toString()

Returns the string representation of this bit set. This consists of a comma separated list of the integers in this set surrounded by curly braces. There is a space after each comma. A sample string is thus "{1, 3, 53}".

Returns:- the string representation.

public void xor(BitSet bs)

Performs the logical XOR operation on this bit set and the given`set`

. This means it builds the symmetric remainder of the two sets (the elements that are in one set, but not in the other). The result is stored into this bit set, which grows as necessary.

Parameters:`bs`

- the second bit set

Throws:`NullPointerException`

- if bs is null

BitSet.java -- A vector of bits.
Copyright (C) 1998, 1999, 2000, 2001, 2004, 2005 Free Software Foundation, Inc.
This file is part of GNU Classpath.
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