Small number encoder

foo.java

// Writes numbers less than 172 in one byte, numbers less than 1936 in 2 bytes.  
private static void writeInt(OutputStream os, int i) throws IOException {
    if (i < 0) {
      throw new UnsupportedOperationException("no neg");
    } else if (i < 172) {
      os.write((byte) i);
    } else if (i < 1936) {
      i -= 172;
      os.write((byte)(172 + 42 + (i % 42)));
      os.write((byte)(172 + (i / 42)));
    } else {
      throw new UnsupportedOperationException("too big");
    }
  }
  
  @Test
  public void run() throws IOException {
    var baos = new ByteArrayOutputStream();
    List<Integer> ints = new ArrayList<>();
    SplittableRandom s = new SplittableRandom(1);
    for (int i = 0; i < 10_000; i++) {
      final double mean = 150;
      final double max = 1936;
      var r = -Math.log(s.nextDouble(Math.nextUp(0.0), 1)) * mean;
      ints.add(Math.toIntExact(Math.round(Math.max(Math.min(max, r), 0))));
    }
    for (Integer i : ints) {
      writeInt(baos, i);
    }
    System.out.println(baos.size());
  }