This version uses the SetOfInts ADT.

public class Filter
{
  public static void main(String[] args)
  {
    int[] keys = StdIn.readInts(args[0]);
    SetOfInts s = new SetOfInts(keys);

    while(!StdIn.isEmpty()) {
      int item = Stdin.readInt();
      if (!s.contains(item) ) {
         System.out.println(item);
      }
    }
  }
}