If you need to use DeciamlFormat you could use:
int input = 893;
DecimalFormat decFormat = new DecimalFormat("000000"); //as many palces as you need
String output = decFormat.format(input);
And then replace all leading zeros with + sign.
String.format("%06d", input); //also gives you leading zeros
You still have to check if the output is too long, if you always want 6 places.