Why XOR value is empty in BitSet in java?

May 29, 2022

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.

>Solution :

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 {}