This is the signature for the method:
format is your first argument, args your second one. About your last argument printf doesn't care.
Also, your second argument,
"13%1$s", is taken as a
String. So
"%1$s" is here not a placeholder
for anything.
What is done in the end? printf checks the first argument; prints
12, then gets the second argument and prints
13%1$s. Altogether:
1213%1$s
Hope that helps,
cheers
Bob