Package org.jmol.util

Class BitSet

java.lang.Object

org.jmol.util.BitSet

All Implemented Interfaces:

java.lang.Cloneable

public class BitSet
extends java.lang.Object
implements java.lang.Cloneable

a fast 64-bit BitSet optimized for Java2Script -- about 25 times faster than java.util.BitSet in JavaScript

Since:

JDK1.0

Constructor Summary

Constructors

Constructor	Description
BitSet()	Creates a new bit set.

Method Summary

Modifier and Type	Method	Description
void	and(BitSet set)	Performs a logical AND of this target bit set with the argument bit set.
void	andNot(BitSet set)	Clears all of the bits in this BitSet whose corresponding bit is set in the specified BitSet.
int	cardinality()	Returns the number of bits set to true in this BitSet.
int	cardinalityN(int max)
void	clear(int bitIndex)	Sets the bit specified by the index to false.
void	clearAll()	Sets all of the bits in this BitSet to false.
void	clearBits(int fromIndex, int toIndex)	Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to false.
java.lang.Object	clone()	Cloning this BitSet produces a new BitSet that is equal to it.
boolean	equals(java.lang.Object obj)	Compares this object against the specified object.
boolean	get(int bitIndex)	Returns the value of the bit with the specified index.
int	hashCode()	Returns a hash code value for this bit set.
boolean	intersects(BitSet set)	Returns true if the specified BitSet has any bits set to true that are also set to true in this BitSet.
boolean	isEmpty()	Returns true if this BitSet contains no bits that are set to true.
int	length()	Returns the "logical size" of this BitSet: the index of the highest set bit in the BitSet plus one.
static BitSet	newN(int nbits)	Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range 0 through nbits-1.
int	nextClearBit(int fromIndex)	Returns the index of the first bit that is set to false that occurs on or after the specified starting index.
int	nextSetBit(int fromIndex)	Returns the index of the first bit that is set to true that occurs on or after the specified starting index.
void	or(BitSet set)	Performs a logical OR of this bit set with the bit set argument.
void	set(int bitIndex)	Sets the bit at the specified index to true.
void	setBits(int fromIndex, int toIndex)	Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to true.
void	setBitTo(int bitIndex, boolean value)	Sets the bit at the specified index to the specified value.
int	size()	Returns the number of bits of space actually in use by this BitSet to represent bit values.
java.lang.String	toString()	Returns a string representation of this bit set.
void	xor(BitSet set)	Performs a logical XOR of this bit set with the bit set argument.

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

BitSet

public BitSet()

Creates a new bit set. All bits are initially false.

Method Detail

newN

public static BitSet newN(int nbits)

Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range 0 through nbits-1. All bits are initially false.

Parameters:

nbits - the initial size of the bit set

Returns:

bs

Throws:

java.lang.NegativeArraySizeException - if the specified initial size is negative

set

public void set(int bitIndex)

Sets the bit at the specified index to true.

Parameters:

bitIndex - a bit index

Throws:

java.lang.IndexOutOfBoundsException - if the specified index is negative

Since:

JDK1.0

setBitTo

public void setBitTo(int bitIndex,
                     boolean value)

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

Parameters:

bitIndex - a bit index

value - a boolean value to set

Throws:

java.lang.IndexOutOfBoundsException - if the specified index is negative

Since:

1.4

setBits

public void setBits(int fromIndex,
                    int toIndex)

Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to true.

Parameters:

fromIndex - index of the first bit to be set

toIndex - index after the last bit to be set

Throws:

java.lang.IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex

Since:

1.4

clear

public void clear(int bitIndex)

Sets the bit specified by the index to false.

Parameters:

bitIndex - the index of the bit to be cleared

Throws:

java.lang.IndexOutOfBoundsException - if the specified index is negative

Since:

JDK1.0

clearBits

public void clearBits(int fromIndex,
                      int toIndex)

Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to false.

Parameters:

fromIndex - index of the first bit to be cleared

toIndex - index after the last bit to be cleared

Throws:

java.lang.IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex

Since:

1.4

clearAll

public void clearAll()

Sets all of the bits in this BitSet to false.

Since:

1.4

get

public boolean get(int bitIndex)

Returns the value of the bit with the specified index. The value is true if the bit with the index bitIndex is currently set in this BitSet; otherwise, the result is false.

Parameters:

bitIndex - the bit index

Returns:

the value of the bit with the specified index

Throws:

java.lang.IndexOutOfBoundsException - if the specified index is negative

nextSetBit

public int nextSetBit(int fromIndex)

Returns the index of the first bit that is set to true that occurs on or after the specified starting index. If no such bit exists then -1 is returned.

To iterate over the true bits in a BitSet, use the following loop:

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

Parameters:

fromIndex - the index to start checking from (inclusive)

Returns:

the index of the next set bit, or -1 if there is no such bit

Throws:

java.lang.IndexOutOfBoundsException - if the specified index is negative

Since:

1.4

nextClearBit

public int nextClearBit(int fromIndex)

Returns the index of the first bit that is set to false that occurs on or after the specified starting index.

Parameters:

fromIndex - the index to start checking from (inclusive)

Returns:

the index of the next clear bit

Throws:

java.lang.IndexOutOfBoundsException - if the specified index is negative

Since:

1.4

length

public int length()

Returns the "logical size" of this BitSet: the index of the highest set bit in the BitSet plus one. Returns zero if the BitSet contains no set bits.

Returns:

the logical size of this BitSet

Since:

1.2

isEmpty

public boolean isEmpty()

Returns true if this BitSet contains no bits that are set to true.

Returns:

boolean indicating whether this BitSet is empty

Since:

1.4

intersects

public boolean intersects(BitSet set)

Returns true if the specified BitSet has any bits set to true that are also set to true in this BitSet.

Parameters:

set - BitSet to intersect with

Returns:

boolean indicating whether this BitSet intersects the specified BitSet

Since:

1.4

cardinality

public int cardinality()

Returns the number of bits set to true in this BitSet.

Returns:

the number of bits set to true in this BitSet

Since:

1.4

and

public void and(BitSet set)

Performs a logical AND of this target bit set with the argument bit set. This bit set is modified so that each bit in it has the value true if and only if it both initially had the value true and the corresponding bit in the bit set argument also had the value true.

Parameters:

set - a bit set

or

public void or(BitSet set)

Performs a logical OR of this bit set with the bit set argument. This bit set is modified so that a bit in it has the value true if and only if it either already had the value true or the corresponding bit in the bit set argument has the value true.

Parameters:

set - a bit set

xor

public void xor(BitSet set)

Performs a logical XOR of this bit set with the bit set argument. This bit set is modified so that a bit in it has the value true if and only if one of the following statements holds:

• The bit initially has the value true, and the corresponding bit in the argument has the value false.
• The bit initially has the value false, and the corresponding bit in the argument has the value true.

Parameters:

set - a bit set

andNot

public void andNot(BitSet set)

Clears all of the bits in this BitSet whose corresponding bit is set in the specified BitSet.

Parameters:

set - the BitSet with which to mask this BitSet

Since:

1.2

hashCode

public int hashCode()

Returns a hash code value for this bit set. The hash code depends only on which bits have been set within this BitSet. The algorithm used to compute it may be described as follows.

Suppose the bits in the BitSet were to be stored in an array of long integers called, say, words, in such a manner that bit k is set in the BitSet (for nonnegative values of k) if and only if the expression

 ((k >> 6) < words.length) && ((words[k >> 6] & (1L << (bit & 0x3F))) != 0)
 

is true. 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 = words.length; --i >= 0;) {
    h ˆ= words[i] * (i + 1);
  }
  return (int) ((h >> 32) ˆ h);
 }
 

Note that the hash code values change if the set of bits is altered.

Overrides the hashCode method of Object.

Overrides:

hashCode in class java.lang.Object

Returns:

a hash code value for this bit set.

size

public int size()

Returns the number of bits of space actually in use by this BitSet to represent bit values. The maximum element in the set is the size - 1st element.

Returns:

the number of bits currently in this bit set

equals

public boolean equals(java.lang.Object obj)

Compares this object against the specified object. The result is true if and only if the argument is not null and is a Bitset object that has exactly the same set of bits set to true as this bit set. That is, for every nonnegative int index k,

 ((BitSet) obj).get(k) == this.get(k)
 

must be true. The current sizes of the two bit sets are not compared.

Overrides:

equals in class java.lang.Object

Parameters:

obj - the object to compare with

Returns:

true if the objects are the same; false otherwise

See Also:

size()

clone

public java.lang.Object clone()

Cloning this BitSet produces a new BitSet that is equal to it. The clone of the bit set is another bit set that has exactly the same bits set to true as this bit set.

Overrides:

clone in class java.lang.Object

Returns:

a clone of this bit set

See Also:

size()

toString

public java.lang.String toString()

Returns a string representation of this bit set. For every index for which this BitSet contains a bit in the set state, the decimal representation of that index is included in the result. Such indices are listed in order from lowest to highest, separated by ", " (a comma and a space) and surrounded by braces, resulting in the usual mathematical notation for a set of integers.

Example:

 BitSet drPepper = new BitSet();
 

Now drPepper.toString() returns empty braces.

 drPepper.set(2);
 

Now drPepper.toString() returns "{2}".

 drPepper.set(4);
 drPepper.set(10);
 

Now drPepper.toString() returns "{2, 4, 10}".

Overrides:

toString in class java.lang.Object

Returns:

a string representation of this bit set

cardinalityN

public int cardinalityN(int max)

Parameters:

max -

Returns:

n bits below max