How does the bitwise complement operator (~ tilde) work?

Question

Why is it that ~2 is equal to -3? How does ~ operator work?

Answer 1

int a=4; System.out.println(~a); Result would be :-5

'~' of any integer in java represents 1's complement of the no. for example i am taking ~4,which means in binary representation 0100. first , length of an integer is four bytes,i.e 4*8(8 bits for 1 byte)=32. So in system memory 4 is represented as 0000 0000 0000 0000 0000 0000 0000 0100 now ~ operator will perform 1's complement on the above binary no

i.e 1111 1111 1111 1111 1111 1111 1111 1011->1's complement the most significant bit represents sign of the no(either - or +) if it is 1 then sign is '-' if it is 0 then sign is '+' as per this our result is a negative number, in java the negative numbers are stored in 2's complement form, the acquired result we have to convert into 2's complement( first perform 1's complement and just add 1 to 1's complement). all the one will become zeros,except most significant bit 1(which is our sign representation of the number,that means for remaining 31 bits 1111 1111 1111 1111 1111 1111 1111 1011 (acquired result of ~ operator) 1000 0000 0000 0000 0000 0000 0000 0100 (1's complement)

1 (2's complement)

1000 0000 0000 0000 0000 0000 0000 0101 now the result is -5 check out this link for the video <[Bit wise operators in java] https://youtu.be/w4pJ4cGWe9Y