data_structures_free

net/datastructures/ElementIterator.java

@@ -0,0 +1,45 @@
+package net.datastructures;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.lang.UnsupportedOperationException;
+
+/**
+ *  A simple iterator class for lists.  The elements of a list are
+ *  returned by this iterator.  No copy of the list is made, so any
+ *  changes to the list are reflected in the iterator.
+ *
+ *  @author Michael Goodrich, Eric Zamore, Roberto Tamassia
+ */
+//begin#fragment Iterator
+public class ElementIterator<E> implements Iterator<E> {
+  protected PositionList<E> list; // the underlying list
+  protected Position<E> cursor; // the next position
+  /** Creates an element iterator over the given list. */
+  public ElementIterator(PositionList<E> L) {
+    list = L;
+    cursor = (list.isEmpty())? null : list.first();
+  }
+//end#fragment Iterator
+  /** Returns whether the iterator has a next object. */
+//begin#fragment Iterator
+  public boolean hasNext() { return (cursor != null);  }
+//end#fragment Iterator
+  /** Returns the next object in the iterator. */
+//begin#fragment Iterator
+  public E next() throws NoSuchElementException {
+    if (cursor == null)
+      throw new NoSuchElementException("No next element");
+    E toReturn = cursor.element();
+    cursor = (cursor == list.last())? null : list.next(cursor);
+    return toReturn;
+  }
+//end#fragment Iterator
+  /** Throws an {@link UnsupportedOperationException} in all cases,
+   * because removal is not a supported operation in this iterator.
+   */
+  public void remove() throws UnsupportedOperationException {
+    throw new UnsupportedOperationException("remove");
+  }
+//begin#fragment Iterator
+}
+//end#fragment Iterator