How does ~ operator works in Java?

Question

I was looking for some bit-Operations in Java and found the ~ operator. I found following explenation:

~a results from a, by inverting all bits of a

So when I make a System.out.println(~1), why is the output -2? As 0001 = 1 after inverting it should be 1110

But 11 ... 1110 is -2. You may want to take a look how negative numbers work — Ecto, Aug 27 '20 at 12:27
You are right, because a negative number can be filled up with 1 I totally forgot about that! — forty4seven, Aug 27 '20 at 12:30

WJS · Answer 1 · 2020-08-27T13:09:27.063

Just remember that negative numbers are stored in two's complement representation. So that means you first take the complement of the number and then add 1.

int val = 20;
val = (~val)+1;
//  20     ==   0b00000000000000000000000000010100
// ~20     ==   0b11111111111111111111111111101011
// (~20)+1 ==   0b11111111111111111111111111101100 
System.out.println(val);

Prints

-20

And whether the value is an integer or floating point, the high order bit is the sign bit. 1 means negative, 0 means not negative.

How does ~ operator works in Java?

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