public void andNot(BitSet set) {
// a & !a is false
if (this == set) {
// all falses result in an empty BitSet
clear();
return;
}
// trim the second set to avoid extra work
trimToSize(array);
int length = array.length();
// truth table
//
// case | a | b | !b | a & !b | change?
// 1 | false | false | true | false | a is already false
// 2 | false | true | false | false | a is already false
// 3 | true | false | true | true | a is already true
// 4 | true | true | false | false | set a to false
//
// we only need to change something in case 4
// whenever b is true, a should be false, so iterate over set b
int index = 0;
while ((index = nextSetWord(set.array, index)) != -1) {
setWord(array, index, getWord(array, index) & ~set.array.get(index));
if (++index >= length) {
// nothing further will affect anything
break;
}
}
}
public int nextSetBit(int fromIndex) {
checkIndex(fromIndex);
int index = wordIndex(fromIndex);
// check the current word
int word = getWord(array, index);
if (word != 0) {
for (int i = bitOffset(fromIndex); i < 32; i++) {
if ((word & (1 << i)) != 0) {
return (bitIndex(index)) + i;
}
}
}
index++;
// find the next set word
trimToSize(array);
index = nextSetWord(array, index);
if (index == -1) {
return -1;
}
// return the next set bit
return (bitIndex(index)) + Integer.numberOfTrailingZeros(array.get(index));
};
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++;
}
}