Bitwise operator for simply flipping all bits in an integer?

java binary bit-manipulation bit bitwise-operators

The ~ unary operator is bitwise negation. If you need fewer bits than what fits in an int then you'll need to mask it with & after the fact.

java binary bit-manipulation bit bitwise-operators

Simply use the bitwise not operator ~.

int flipBits(int n) {    return ~n;}

To use the k least significant bits, convert it to the right mask.
(I assume you want at least 1 bit of course, that's why mask starts at 1)

int flipBits(int n, int k) {    int mask = 1;    for (int i = 1; i < k; ++i)        mask |= mask << 1;    return ~n & mask;}

As suggested by Lưu Vĩnh Phúc, one can create the mask as (1 << k) - 1 instead of using a loop.

int flipBits2(int n, int k) {    int mask = (1 << k) - 1;    return ~n & mask;}

java binary bit-manipulation bit bitwise-operators

There is a number of ways to flip all the bit using operations

x = ~x; // has been mentioned and the most obvious solution.x = -x - 1; or x = -1 * (x + 1);x ^= -1; or x = x ^ ~0;

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