completed iterator methods and classes for ArrayIntList.java and Link…

…edIntList.java

src/ArrayIntList.java

@@ -233,15 +233,15 @@ public void clear()
     @Override
     public Iterator<Integer> iterator()
     {
-        return null;
+        return new IntListIterator();
     }
 
     //create private helper iterator class
-    private class intListIterator implements Iterator<Integer>
+    private class IntListIterator implements Iterator<Integer>
     {
         private int i;
 
-        public intListIterator()
+        public IntListIterator()
         {
             i = 0;
         }

src/LinkedIntList.java

@@ -145,7 +145,7 @@ public boolean isEmpty()
     @Override
     public int size()
     {
-        return 0;
+        return size;
     }
 
     /**
@@ -161,6 +161,31 @@ public void clear()
     @Override
     public Iterator<Integer> iterator()
     {
-        return null;
+        return new SinglyLinkedIterator();
+    }
+
+    //helper class that defines how the iterator works
+    private class SinglyLinkedIterator implements Iterator<Integer>
+    {
+        private Node curr;
+
+        public SinglyLinkedIterator()
+        {
+            curr = head;
+        }
+
+        @Override
+        public boolean hasNext()
+        {
+            return curr.next != null;
+        }
+
+        @Override
+        public Integer next()
+        {
+            curr = curr.next;
+
+            return curr.data;
+        }
     }
 }