java.lang.Object java.util.BitSet
public class BitSet
This class implements a vector of bits that grows as needed. Each component of the bit set has a boolean value. The bits of a BitSet are indexed by nonnegative integers. Individual indexed bits can be examined, set, or cleared. One BitSet may be used to modify the contents of another BitSet through logical AND, logical inclusive OR, and logical exclusive OR operations.
By default, all bits in the set initially have the value false.
Every bit set has a current size, which is the number of bits of space currently in use by the bit set. Note that the size is related to the implementation of a bit set, so it may change with implementation. The length of a bit set relates to logical length of a bit set and is defined independently of implementation.
Unless otherwise noted, passing a null parameter to any of the methods in a BitSet will result in a NullPointerException.
A BitSet is not safe for multithreaded use without external synchronization.
BitSet()
BitSet(int nbits)
0 through nbits-1. Method Summary void and(BitSet set)
void andNot(BitSet set)
BitSet whose corresponding bit is set in the specified BitSet. int cardinality()
BitSet. void clear()
false. void clear(int bitIndex)
false. void clear(int fromIndex, int toIndex)
false. Object clone()
BitSet produces a new BitSet that is equal to it. boolean equals(Object obj)
void flip(int bitIndex)
void flip(int fromIndex, int toIndex)
boolean get(int bitIndex)
BitSet get(int fromIndex, int toIndex)
int hashCode()
boolean intersects(BitSet set)
BitSet has any bits set to true that are also set to true in this BitSet. boolean isEmpty()
BitSet contains no bits that are set to true. int length()
BitSet: the index of the highest set bit in the BitSet plus one. int nextClearBit(int fromIndex)
false that occurs on or after the specified starting index. int nextSetBit(int fromIndex)
true that occurs on or after the specified starting index. void or(BitSet set)
void set(int bitIndex)
true. void set(int bitIndex, boolean value)
void set(int fromIndex, int toIndex)
true. void set(int fromIndex, int toIndex, boolean value)
int size()
BitSet to represent bit values. String toString()
void xor(BitSet set)
public BitSet()
false.
public BitSet(int nbits)
0 through nbits-1. All bits are initially false.
nbits - the initial size of the bit set.
NegativeArraySizeException - if the specified initial size is negative.
public void flip(int bitIndex)
bitIndex - the index of the bit to flip.
IndexOutOfBoundsException - if the specified index is negative.
public void flip(int fromIndex,
int toIndex)
fromIndex - index of the first bit to flip.
toIndex - index after the last bit to flip.
IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex.
public void set(int bitIndex)
true.
bitIndex - a bit index.
IndexOutOfBoundsException - if the specified index is negative.
public void set(int bitIndex,
boolean value)
bitIndex - a bit index.
value - a boolean value to set.
IndexOutOfBoundsException - if the specified index is negative.
public void set(int fromIndex,
int toIndex)
true.
fromIndex - index of the first bit to be set.
toIndex - index after the last bit to be set.
IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex.
public void set(int fromIndex,
int toIndex,
boolean value)
fromIndex - index of the first bit to be set.
toIndex - index after the last bit to be set
value - value to set the selected bits to
IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex.
public void clear(int bitIndex)
false.
bitIndex - the index of the bit to be cleared.
IndexOutOfBoundsException - if the specified index is negative.
public void clear(int fromIndex,
int toIndex)
false.
fromIndex - index of the first bit to be cleared.
toIndex - index after the last bit to be cleared.
IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex.
public void clear()
false.
public boolean get(int bitIndex)
true if the bit with the index bitIndex is currently set in this BitSet; otherwise, the result is false.
bitIndex - the bit index.
IndexOutOfBoundsException - if the specified index is negative.
public BitSet get(int fromIndex,
int toIndex)
fromIndex - index of the first bit to include.
toIndex - index after the last bit to include.
IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex.
public int nextSetBit(int fromIndex)
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
}
fromIndex - the index to start checking from (inclusive).
IndexOutOfBoundsException - if the specified index is negative.
public int nextClearBit(int fromIndex)
false that occurs on or after the specified starting index.
fromIndex - the index to start checking from (inclusive).
IndexOutOfBoundsException - if the specified index is negative.
public int length()
BitSet: the index of the highest set bit in the BitSet plus one. Returns zero if the BitSet contains no set bits.
BitSet.
public boolean isEmpty()
BitSet contains no bits that are set to true.
BitSet is empty.
public boolean intersects(BitSet set)
BitSet has any bits set to true that are also set to true in this BitSet.
set - BitSet to intersect with
BitSet intersects the specified BitSet.
public int cardinality()
BitSet.
BitSet.
public void and(BitSet set)
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.
set - a bit set.
public void or(BitSet set)
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.
set - a bit set.
public void xor(BitSet set)
true if and only if one of the following statements holds:
true, and the corresponding bit in the argument has the value false.false, and the corresponding bit in the argument has the value true.set - a bit set.
public void andNot(BitSet set)
BitSet whose corresponding bit is set in the specified BitSet.
set - the BitSet with which to mask this BitSet.
public int hashCode()
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 ^= words[i] * (i + 1);
}
return (int)((h >> 32) ^ h);
} Note that the hash code values change if the set of bits is altered.
Overrides the hashCode method of Object.
hashCode in class Object
Object.equals(java.lang.Object), Hashtable
public int size()
BitSet to represent bit values. The maximum element in the set is the size - 1st element.
public boolean equals(Object obj)
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 the equals method of Object.
equals in class Object
obj - the object to compare with.
true if the objects are the same; false otherwise.
size()
public Object clone()
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 the clone method of Object.
clone in class Object
size()
public String toString()
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.
Overrides the toString method of Object.
Example:
BitSet drPepper = new BitSet();Now
drPepper.toString() returns "{}".
drPepper.set(2);Now
drPepper.toString() returns "{2}".
drPepper.set(4); drPepper.set(10);Now
drPepper.toString() returns "{2, 4, 10}".
toString in class Object
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