// Tyler Mi
// Program showing the limitations and uses of for-each loops and iterators
import java.util.*;

public class ForEach {
   public static void main(String[] args) {
      List<Integer> list = new ArrayList<>();
      list.add(1);
      list.add(2);
      list.add(3);
      
      // How we would use a for-each loop to print all the elements
      for (int n : list) {
         System.out.println(n);
         // Unfortunatly, we can't add/remove elements from the structure
         // we are looping over in a for-each loop. This will run into a 
         // ConcurrentModificationException :(
         list.add(2 * n);
      }
   
      // With lists, we can use a normal for-loop though!
      int size = list.size();
      for (int i = 0; i < size; i++) {
         list.add(2 * list.get(i));
      }
      System.out.println(list);
      
      Set<Integer> set = new TreeSet<>();
      set.addAll(list);
      System.out.println(set);
      
      // Like with Lists, we will also run into a ConcurrentModificationException
      // if we try to remove the even numbers from the set as we got through it
      for (int n : set) {
         if (n % 2 == 0) {
            set.remove(n);
         }
      }
      
      // All collections have an .iterator() method that will
      // give you an Iterator over that data-structure
      // Iterators will allow you to get all the elements of the structure
      // like a Scanner, and allow you to remove elements too as you go!
      Iterator<Integer> i = set.iterator();
      while(i.hasNext()) {
         int n = i.next();
         if (n % 2 == 0) {
            // Asking the set to remove it won't work, but we can
            // make the Iterator remove it for us!
            // set.remove(n);
            i.remove();
         }
      }
      System.out.println(set);
   }
}