libjava/java/util/AbstractSequentialList.java

   1 /* AbstractSequentialList.java -- List implementation for sequential access
   2    Copyright (C) 1998, 1999, 2000, 2001, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.util;
  40
  41 /**
  42  * Abstract superclass to make it easier to implement the List interface when
  43  * backed by a sequential-access store, such as a linked list. For random
  44  * access data, use AbstractList. This class implements the random access
  45  * methods (<code>get</code>, <code>set</code>, <code>add</code>, and
  46  * <code>remove</code>) atop the list iterator, opposite of AbstractList's
  47  * approach of implementing the iterator atop random access.
  48  * <p>
  49  *
  50  * To implement a list, you need an implementation for <code>size()</code>
  51  * and <code>listIterator</code>.  With just <code>hasNext</code>,
  52  * <code>next</code>, <code>hasPrevious</code>, <code>previous</code>,
  53  * <code>nextIndex</code>, and <code>previousIndex</code>, you have an
  54  * unmodifiable list. For a modifiable one, add <code>set</code>, and for
  55  * a variable-size list, add <code>add</code> and <code>remove</code>.
  56  * <p>
  57  *
  58  * The programmer should provide a no-argument constructor, and one that
  59  * accepts another Collection, as recommended by the Collection interface.
  60  * Unfortunately, there is no way to enforce this in Java.
  61  *
  62  * @author Original author unknown
  63  * @author Bryce McKinlay
  64  * @author Eric Blake (ebb9@email.byu.edu)
  65  * @see Collection
  66  * @see List
  67  * @see AbstractList
  68  * @see AbstractCollection
  69  * @see ListIterator
  70  * @see LinkedList
  71  * @since 1.2
  72  * @status updated to 1.4
  73  */
  74 public abstract class AbstractSequentialList extends AbstractList
  75 {
  76   /**
  77    * The main constructor, for use by subclasses.
  78    */
  79   protected AbstractSequentialList()
  80   {
  81   }
  82
  83   /**
  84    * Returns a ListIterator over the list, starting from position index.
  85    * Subclasses must provide an implementation of this method.
  86    *
  87    * @param index the starting position of the list
  88    * @return the list iterator
  89    * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt; size()
  90    */
  91   public abstract ListIterator listIterator(int index);
  92
  93   /**
  94    * Insert an element into the list at a given position (optional operation).
  95    * This shifts all existing elements from that position to the end one
  96    * index to the right. This version of add has no return, since it is
  97    * assumed to always succeed if there is no exception. This iteration
  98    * uses listIterator(index).add(o).
  99    *
 100    * @param index the location to insert the item
 101    * @param o the object to insert
 102    * @throws UnsupportedOperationException if this list does not support the
 103    *         add operation
 104    * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt; size()
 105    * @throws ClassCastException if o cannot be added to this list due to its
 106    *         type
 107    * @throws IllegalArgumentException if o cannot be added to this list for
 108    *         some other reason.
 109    * @throws NullPointerException if o is null and the list does not permit
 110    *         the addition of null values.
 111    */
 112   public void add(int index, Object o)
 113   {
 114     listIterator(index).add(o);
 115   }
 116
 117   /**
 118    * Insert the contents of a collection into the list at a given position
 119    * (optional operation). Shift all elements at that position to the right
 120    * by the number of elements inserted. This operation is undefined if
 121    * this list is modified during the operation (for example, if you try
 122    * to insert a list into itself).
 123    * <p>
 124    *
 125    * This implementation grabs listIterator(index), then proceeds to use add
 126    * for each element returned by c's iterator. Sun's online specs are wrong,
 127    * claiming that this also calls next(): listIterator.add() correctly
 128    * skips the added element.
 129    *
 130    * @param index the location to insert the collection
 131    * @param c the collection to insert
 132    * @return true if the list was modified by this action, that is, if c is
 133    *         non-empty
 134    * @throws UnsupportedOperationException if this list does not support the
 135    *         addAll operation
 136    * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt; size()
 137    * @throws ClassCastException if some element of c cannot be added to this
 138    *         list due to its type
 139    * @throws IllegalArgumentException if some element of c cannot be added
 140    *         to this list for some other reason
 141    * @throws NullPointerException if the specified collection is null
 142    * @throws NullPointerException if an object, o, in c is null and the list
 143    *         does not permit the addition of null values.
 144    * @see #add(int, Object)
 145    */
 146   public boolean addAll(int index, Collection c)
 147   {
 148     Iterator ci = c.iterator();
 149     int size = c.size();
 150     ListIterator i = listIterator(index);
 151     for (int pos = size; pos > 0; pos--)
 152       i.add(ci.next());
 153     return size > 0;
 154   }
 155
 156   /**
 157    * Get the element at a given index in this list. This implementation
 158    * returns listIterator(index).next().
 159    *
 160    * @param index the index of the element to be returned
 161    * @return the element at index index in this list
 162    * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt;= size()
 163    */
 164   public Object get(int index)
 165   {
 166     // This is a legal listIterator position, but an illegal get.
 167     if (index == size())
 168       throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
 169                                           + size());
 170     return listIterator(index).next();
 171   }
 172
 173   /**
 174    * Obtain an Iterator over this list, whose sequence is the list order. This
 175    * implementation returns listIterator().
 176    *
 177    * @return an Iterator over the elements of this list, in order
 178    */
 179   public Iterator iterator()
 180   {
 181     return listIterator();
 182   }
 183
 184   /**
 185    * Remove the element at a given position in this list (optional operation).
 186    * Shifts all remaining elements to the left to fill the gap. This
 187    * implementation uses listIterator(index) and ListIterator.remove().
 188    *
 189    * @param index the position within the list of the object to remove
 190    * @return the object that was removed
 191    * @throws UnsupportedOperationException if this list does not support the
 192    *         remove operation
 193    * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt;= size()
 194    */
 195   public Object remove(int index)
 196   {
 197     // This is a legal listIterator position, but an illegal remove.
 198     if (index == size())
 199       throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
 200                                           + size());
 201     ListIterator i = listIterator(index);
 202     Object removed = i.next();
 203     i.remove();
 204     return removed;
 205   }
 206
 207   /**
 208    * Replace an element of this list with another object (optional operation).
 209    * This implementation uses listIterator(index) and ListIterator.set(o).
 210    *
 211    * @param index the position within this list of the element to be replaced
 212    * @param o the object to replace it with
 213    * @return the object that was replaced
 214    * @throws UnsupportedOperationException if this list does not support the
 215    *         set operation
 216    * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt;= size()
 217    * @throws ClassCastException if o cannot be added to this list due to its
 218    *         type
 219    * @throws IllegalArgumentException if o cannot be added to this list for
 220    *         some other reason
 221    * @throws NullPointerException if o is null and the list does not allow
 222    *         a value to be set to null.
 223    */
 224   public Object set(int index, Object o)
 225   {
 226     // This is a legal listIterator position, but an illegal set.
 227     if (index == size())
 228       throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
 229                                           + size());
 230     ListIterator i = listIterator(index);
 231     Object old = i.next();
 232     i.set(o);
 233     return old;
 234   }
 235 }