Exemple

public static void main( String[] args ) {
for ( int i = 0; i < args.length; i++ ) {
if (! Character.isDigit(args[i].charAt(0))) {
System.out.println("Pas un chiffre");
} else {
System.out.println("Un chiffre");
}
}
}

Solution
  1. Supprimez la négation.
  2. Intervertissez les parties if et else.

public static void main( String[] args ) {
for ( int i = 0; i < args.length; i++ ) {
if (Character.isDigit(args[i].charAt(0))) {
System.out.println("Un chiffre");
} else {
System.out.println("Pas un chiffre");
}
}
}