Here is how my method is currently defined in Scala, i've been following [this Stackoverflow answer](https://stackoverflow.com/a/275715/967713)

```
  def digitFormatter(long: Long, numDigits: Int): String = {
    String.format(s"%0${numDigits}d", long)
  }

```

This seems to work ok with postive integers, i get this expected behavior

```
    assert(digitFormatter(0, 1) == "0")
    assert(digitFormatter(0, 2) == "00")
    assert(digitFormatter(1, 2) == "01")
    assert(digitFormatter(10, 2) == "10")

```

However this doesn't seem to work with negative numbers, this is what I would expect my output to be

```
    assert(
      digitFormatter(-1, 2) == "-01")

```

However the result I get is just `-1`. How do I pad leading zeroes on negative numbers using the java std libraries?