content: /*
   * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.util;
  
  /**
   * An iterator for lists that allows the programmer
   * to traverse the list in either direction, modify
   * the list during iteration, and obtain the iterator's
   * current position in the list. A {@code ListIterator}
   * has no current element; its <I>cursor position</I> always
   * lies between the element that would be returned by a call
   * to {@code previous()} and the element that would be
   * returned by a call to {@code next()}.
   * An iterator for a list of length {@code n} has {@code n+1} possible
   * cursor positions, as illustrated by the carets ({@code ^}) below:
   * <PRE>
   *                      Element(0)   Element(1)   Element(2)   ... Element(n-1)
   * cursor positions:  ^            ^            ^            ^                  ^
   * </PRE>
   * Note that the {@link #remove} and {@link #set(Object)} methods are
   * <i>not</i> defined in terms of the cursor position;  they are defined to
   * operate on the last element returned by a call to {@link #next} or
   * {@link #previous()}.
   *
   * <p>This interface is a member of the
   * <a href="{@docRoot}/../technotes/guides/collections/index.html">
   * Java Collections Framework</a>.
   *
   * @author  Josh Bloch
   * @see Collection
   * @see List
   * @see Iterator
   * @see Enumeration
   * @see List#listIterator()
   * @since   1.2
   */
  public interface ListIterator<E> extends Iterator<E> {
      // Query Operations
  
      /**
       * Returns {@code true} if this list iterator has more elements when
       * traversing the list in the forward direction. (In other words,
       * returns {@code true} if {@link #next} would return an element rather
       * than throwing an exception.)
       *
       * @return {@code true} if the list iterator has more elements when
       *         traversing the list in the forward direction
       */
      boolean hasNext();
  
      /**
       * Returns the next element in the list and advances the cursor position.
       * This method may be called repeatedly to iterate through the list,
       * or intermixed with calls to {@link #previous} to go back and forth.
       * (Note that alternating calls to {@code next} and {@code previous}
       * will return the same element repeatedly.)
       *
       * @return the next element in the list
       * @throws NoSuchElementException if the iteration has no next element
       */
      E next();
  
      /**
       * Returns {@code true} if this list iterator has more elements when
       * traversing the list in the reverse direction.  (In other words,
       * returns {@code true} if {@link #previous} would return an element
       * rather than throwing an exception.)
       *
       * @return {@code true} if the list iterator has more elements when
       *         traversing the list in the reverse direction
       */
      boolean hasPrevious();
  
      /**
       * Returns the previous element in the list and moves the cursor
       * position backwards.  This method may be called repeatedly to
       * iterate through the list backwards, or intermixed with calls to
       * {@link #next} to go back and forth.  (Note that alternating calls
       * to {@code next} and {@code previous} will return the same
       * element repeatedly.)
       *
       * @return the previous element in the list
       * @throws NoSuchElementException if the iteration has no previous
       *         element
       */
      E previous();
  
      /**
       * Returns the index of the element that would be returned by a
       * subsequent call to {@link #next}. (Returns list size if the list
       * iterator is at the end of the list.)
       *
       * @return the index of the element that would be returned by a
       *         subsequent call to {@code next}, or list size if the list
       *         iterator is at the end of the list
       */
      int nextIndex();
  
      /**
       * Returns the index of the element that would be returned by a
       * subsequent call to {@link #previous}. (Returns -1 if the list
       * iterator is at the beginning of the list.)
       *
       * @return the index of the element that would be returned by a
       *         subsequent call to {@code previous}, or -1 if the list
       *         iterator is at the beginning of the list
       */
      int previousIndex();
  
  
      // Modification Operations
  
      /**
       * Removes from the list the last element that was returned by {@link
       * #next} or {@link #previous} (optional operation).  This call can
       * only be made once per call to {@code next} or {@code previous}.
       * It can be made only if {@link #add} has not been
       * called after the last call to {@code next} or {@code previous}.
       *
       * @throws UnsupportedOperationException if the {@code remove}
       *         operation is not supported by this list iterator
       * @throws IllegalStateException if neither {@code next} nor
       *         {@code previous} have been called, or {@code remove} or
       *         {@code add} have been called after the last call to
       *         {@code next} or {@code previous}
       */
      void remove();
  
      /**
       * Replaces the last element returned by {@link #next} or
       * {@link #previous} with the specified element (optional operation).
       * This call can be made only if neither {@link #remove} nor {@link
       * #add} have been called after the last call to {@code next} or
       * {@code previous}.
       *
       * @param e the element with which to replace the last element returned by
       *          {@code next} or {@code previous}
       * @throws UnsupportedOperationException if the {@code set} operation
       *         is not supported by this list iterator
       * @throws ClassCastException if the class of the specified element
       *         prevents it from being added to this list
       * @throws IllegalArgumentException if some aspect of the specified
       *         element prevents it from being added to this list
       * @throws IllegalStateException if neither {@code next} nor
       *         {@code previous} have been called, or {@code remove} or
       *         {@code add} have been called after the last call to
       *         {@code next} or {@code previous}
       */
      void set(E e);
  
      /**
       * Inserts the specified element into the list (optional operation).
       * The element is inserted immediately before the element that
       * would be returned by {@link #next}, if any, and after the element
       * that would be returned by {@link #previous}, if any.  (If the
       * list contains no elements, the new element becomes the sole element
       * on the list.)  The new element is inserted before the implicit
       * cursor: a subsequent call to {@code next} would be unaffected, and a
       * subsequent call to {@code previous} would return the new element.
       * (This call increases by one the value that would be returned by a
       * call to {@code nextIndex} or {@code previousIndex}.)
       *
       * @param e the element to insert
       * @throws UnsupportedOperationException if the {@code add} method is
       *         not supported by this list iterator
       * @throws ClassCastException if the class of the specified element
       *         prevents it from being added to this list
       * @throws IllegalArgumentException if some aspect of this element
       *         prevents it from being added to this list
       */
      void add(E e);
  }
  