I tried System.out.printf("Primes up to %8d %8d\n", m, count); and it worked fine on GCJ (as far as I remember), but someone else got the error 45: error: Can't find method 'printf(Ljava/lang/String;II)' in type 'java.io.PrintStream'. System.out.printf("Primes up to %8d %8d\n", m, count); Is there a reson for this?