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

Question

除了通常的“保持计数器”方法以外，还有什么快速的方法可以计算BitSet中设置的位数？

Answer 1

cardinality（）方法返回设置的位数。

Answer 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

Answer 3

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

Output:

1