単純に scala> def sprintf(fmt:String, args:Any*) = String.format(fmt, args) sprintf: (String,Any*)java.lang.Stringだと scala> sprintf("%d,%d", 1,2) java.util.IllegalFormatConversionException: d != scala.runtime.BoxedObjectArray at java.util.Formatter$FormatSpecifier.failConversion(Formatter.java:3992) at java.util.Formatter$FormatSpecifier.printInteger(Formatter.java:2708) at java.util.Formatter$Format