Java: Count number of bits set in a java.util.BitSet

Any quick method to count the number of set bits in a BitS开发者_如何学JAVAet other than the usual 'keep a counter' method?

The cardinality() method returns the number of set bits.

(Assuming you don't want to call cardinality())

int count = 0; 
for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i+1)) {
    count++;
}

see javadoc

BitSet B1 = new BitSet(3);
B1.set(0);
B1.cardinality();

Output:

1