public void and(BitSet set) {
// a & a is just a
if (this == set) {
return;
}
// trim the second set to avoid extra work
trimToSize(set.array);
// check if the length is longer than otherLength
int otherLength = set.array.length();
if (array.length() > otherLength) {
// shrink the array, effectively ANDing those bits to false
setLengthWords(array, otherLength);
}
// truth table
//
// case | a | b | a & b | change?
// 1 | false | false | false | a is already false
// 2 | false | true | false | a is already false
// 3 | true | false | false | set a to false
// 4 | true | true | true | a is already true
//
// we only need to change something in case 3, so iterate over set a
int index = 0;
while ((index = nextSetWord(array, index)) != -1) {
setWord(array, index, array.get(index) & getWord(set.array, index));
index++;
}
}
public void clear(int fromIndex, int toIndex) {
checkRange(fromIndex, toIndex);
int length = length();
if (fromIndex >= length) {
// nothing to do
return;
}
// check to see if toIndex is greater than our array length
if (toIndex >= length) {
// truncate the array by setting it's length
int newLength = wordIndex(fromIndex + 31);
setLengthWords(array, newLength);
// remove the extra bits off the end
if ((bitIndex(newLength)) - fromIndex != 0) {
maskOutWord(array, newLength - 1, bitOffset(fromIndex), 32);
}
} else {
int first = wordIndex(fromIndex);
int last = wordIndex(toIndex);
int startBit = bitOffset(fromIndex);
int endBit = bitOffset(toIndex);
if (first == last) {
// clear the bits in between first and last
maskOutWord(array, first, startBit, endBit);
} else {
// clear the bits from fromIndex to the next 32 bit boundary
if (startBit != 0) {
maskOutWord(array, first++, startBit, 32);
}
// clear the bits from the last 32 bit boundary to the toIndex
if (endBit != 0) {
maskOutWord(array, last, 0, endBit);
}
//
// delete everything in between
//
for (int i = first; i < last; i++) {
deleteWord(array, i);
}
}
}
}
public BitSet(int nbits) {
this();
// throw an exception to be consistent
// but (do we want to be consistent?)
if (nbits < 0) {
throw new NegativeArraySizeException("nbits < 0: " + nbits);
}
// even though the array's length is loosely kept to that of Sun's
// "logical
// length," this might help in some cases where code uses size() to fill
// in
// bits after constructing a BitSet, or after having one passed in as a
// parameter.
setLengthWords(array, wordIndex(nbits + 31));
}