Format a number with leading sign

Question

How do I format in Java a number with its leading sign?

Negative numbers are correctly displayed with leading -, but obviously positive numbers are not

Answer 1

API for Formatter provides an example:

Formatter formatter = new Formatter();
System.out.println(formatter.format(Locale.FRANCE, "e = %+10.4f", Math.E));
//e =    +2,7183