Why XOR value is empty in BitSet in java?-CodePudding

I just entered into Advance Java. I don't know why xor() function returning empty set. As i know, XOR return zero for two same bits and 1 for two different bits. So, if I XOR first two bit from Bits One and Bits two that is, 0 and 1 respectively, why does it return empty set. Please explain in detail, if possible and/or necessary.

Code

public class LearnBitSet {
public static void main(String[] args) {
BitSet bits1 = new BitSet(32);
BitSet bits2 = new BitSet(32);
for (int bitCount = 0; bitCount < 32; bitCount  ) {
        if (bitCount % 2 == 0){
            bits1.set(bitCount);
        }
        if (bitCount % 5 != 0){
            bits2.set(bitCount);
        }
    }
System.out.println("Bits One = "   bits1);
System.out.println("Bits Two = "   bits2);
// AND
bits1.and(bits2);
System.out.println("ADD = "  bits1);

// OR
bits1.or(bits2);
System.out.println("OR = " bits1);
// XOR

bits1.xor(bits2);
System.out.println("XOR = " bits1);
}

}

OUTPUT

Bits One = {0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30}
Bits Two = {1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 19, 21, 22, 23, 24, 26, 27, 28, 29, 31}
ADD = {2, 4, 6, 8, 12, 14, 16, 18, 22, 24, 26, 28}
OR = {1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 19, 21, 22, 23, 24, 26, 27, 28, 29, 31}
XOR = {}

EDIT 1st Also, there is problem that Cardinality is 0. Why ? In output, there are so many but bits1.cardinality() returns zero. Is there any detailed resource Online to understand BitSet.

CodePudding user response：

You can see that the contents of bits1 are exactly the same as bits2 after you've done the OR operation:

...
Bits Two = {1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 19, 21, 22, 23, 24, 26, 27, 28, 29, 31}
...
OR = {1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 19, 21, 22, 23, 24, 26, 27, 28, 29, 31}

So if you're doing an XOR operation where both operands are the same, you'll get "0" or "False" by definition (see the truth table), or in this case a BitSet with all bits set to false.

Finally, according to the documentation of toString(), an empty BitSet is printed as {}