I have Java methods taking Boolean arguments and I want to test every combination of those. To have our testing framework try those combinations I need to provide it with a two-dimensional array of the n-bit Boolean values. The code I once had is,

final Boolean[][] testArguments = new Boolean[1 << argCount][];
int testNum = 0;
testArguments[testNum] = new Boolean[argCount];
Arrays.fill(testArguments[testNum], false);
while (++testNum < testArguments.length) {
  testArguments[testNum] = Arrays.copyOf(testArguments[testNum - 1], argCount);
  int argNum = argCount - 1;
  while (true) {
    if (testArguments[testNum][argNum]) {
      testArguments[testNum][argNum--] = false;
    } else {
      testArguments[testNum][argNum] = true;
      break;
    }
  }
}
return testArguments;

I thought that was quite neat. However, with advances in both Java and Google's Guava one can now replace all that with,

return Lists.cartesianProduct(Collections.nCopies(argCount, ImmutableList.of(false, true)))
       .stream().map(args -> args.stream().toArray(Boolean[]::new)).toArray(Boolean[][]::new);

Admittedly I doubt that either is easily read.