Fast approximately uniform int sampling algorithm. See "Fast Random Integer Generation in an Interval" by Daniel Lemire for a similar unbiased algorithm.

biased int sampling fragment .java

default int nextInt_Biased(int upperBound)
{
  if (upperBound == 0) { return nextInt(); }
  if (upperBound == 1) { return 0; }

  final long unsignedLimit = upperBound & 0xFFFF_FFFFL;
  final int log2Ceil = 64 - Long.numberOfLeadingZeros(unsignedLimit - 1);
  final int bitsOfRandomness = 64 - log2Ceil;
  final long rand = nextUnsignedLongBits(bitsOfRandomness);
  return (int)(long)((rand * unsignedLimit) >>> bitsOfRandomness);
}