I would place this kind of functioality into class Integer (or maybe
throughout the Number hierarchy) in a more general form like

printOn: aStream base: base length: total padding: aBoolean

and friends

printStringBase: base length: total padding: aBoolean
printString: length
printStringPadded: length
...

So

	1 printStringPadded: 3 -> '001'

would give you what you want and would be open to many other uses cases