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

问题

Any quick method to count the number of set bits in a BitSet other than the usual 'keep a counter' method?

回答1:

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

回答2:

(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

回答3:

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

Output:

1

来源：https://stackoverflow.com/questions/4883172/java-count-number-of-bits-set-in-a-java-util-bitset