code: private static double absDiffOfMeans(double[] A, double[] B, boolean randomize) {
      Random random = new Random();
      double aTotal = 0.0;
      double bTotal = 0.0;
      for (int i = 0; i < A.length; i++) {
        if (randomize && random.nextBoolean()) {
          aTotal += B[i];
          bTotal += A[i];
        } else {
          aTotal += A[i];
          bTotal += B[i];
        }
      }
      double aMean = aTotal / A.length;
      double bMean = bTotal / B.length;
      return Math.abs(aMean - bMean);
    }
docs: Assumes input arrays have equal, non-zero length.