Had to look up >>>. The code you posted probably assumes the arguments are positive numbers. Java really could use unsigned types.

Also, gcc dialect C (with -mpopcnt on Nehalem era or better x86, or whatever's needed on other architectures with a popcount instruction):

int bsr(unsigned a, unsigned b) {
  return __builtin_popcount(a^b);
}

This is probably against the spirit of the question though.