Binary Ones Complement Operator in Java

Question

Why and how does System.out.println(~4); gives output -5 and System.out.println(~0); gives output -1 ?

Answer 1

4 is  00000000 00000000 00000000 00000100

~4 is 11111111 11111111 11111111 11111011 = -5

0 is  00000000 00000000 00000000 00000000

~0 is 11111111 11111111 11111111 11111111 = -1

Answer 2

negation of a number reverses it's bits. But on putting -(negative) sign on number logically it becomes 1+(~x) .

Since -x = 1+(~x) thus (~x) = -x -1

Answer 3

And if you are wondering why

11111111 11111111 11111111 11111011 = -5

you could read more about two's complement and negative numbers:

two's complement