mirror of git://gcc.gnu.org/git/gcc.git
946 lines
23 KiB
Java
946 lines
23 KiB
Java
/* LinkedList.java -- Linked list implementation of the List interface
|
|
Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
|
|
|
|
This file is part of GNU Classpath.
|
|
|
|
GNU Classpath is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 2, or (at your option)
|
|
any later version.
|
|
|
|
GNU Classpath 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 for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with GNU Classpath; see the file COPYING. If not, write to the
|
|
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA.
|
|
|
|
As a special exception, if you link this library with other files to
|
|
produce an executable, this library does not by itself cause the
|
|
resulting executable to be covered by the GNU General Public License.
|
|
This exception does not however invalidate any other reasons why the
|
|
executable file might be covered by the GNU General Public License. */
|
|
|
|
|
|
package java.util;
|
|
import java.io.Serializable;
|
|
import java.io.ObjectOutputStream;
|
|
import java.io.ObjectInputStream;
|
|
import java.io.IOException;
|
|
import java.lang.reflect.Array;
|
|
|
|
/**
|
|
* Linked list implementation of the List interface. In addition to the
|
|
* methods of the List interface, this class provides access to the first
|
|
* and last list elements in O(1) time for easy stack, queue, or double-ended
|
|
* queue (deque) creation. The list is doubly-linked, with traversal to a
|
|
* given index starting from the end closest to the element.<p>
|
|
*
|
|
* LinkedList is not synchronized, so if you need multi-threaded access,
|
|
* consider using:<br>
|
|
* <code>List l = Collections.synchronizedList(new LinkedList(...));</code>
|
|
* <p>
|
|
*
|
|
* The iterators are <i>fail-fast</i>, meaning that any structural
|
|
* modification, except for <code>remove()</code> called on the iterator
|
|
* itself, cause the iterator to throw a
|
|
* {@link ConcurrentModificationException} rather than exhibit
|
|
* non-deterministic behavior.
|
|
*
|
|
* @author Original author unknown
|
|
* @author Bryce McKinlay
|
|
* @author Eric Blake <ebb9@email.byu.edu>
|
|
* @see List
|
|
* @see ArrayList
|
|
* @see Vector
|
|
* @see Collections#synchronizedList(List)
|
|
* @since 1.2
|
|
* @status missing javadoc, but complete to 1.4
|
|
*/
|
|
public class LinkedList extends AbstractSequentialList
|
|
implements List, Cloneable, Serializable
|
|
{
|
|
/**
|
|
* Compatible with JDK 1.2.
|
|
*/
|
|
private static final long serialVersionUID = 876323262645176354L;
|
|
|
|
/**
|
|
* The first element in the list.
|
|
*/
|
|
transient Entry first;
|
|
|
|
/**
|
|
* The last element in the list.
|
|
*/
|
|
transient Entry last;
|
|
|
|
/**
|
|
* The current length of the list.
|
|
*/
|
|
transient int size = 0;
|
|
|
|
/**
|
|
* Class to represent an entry in the list. Holds a single element.
|
|
*/
|
|
private static final class Entry
|
|
{
|
|
/** The element in the list. */
|
|
Object data;
|
|
|
|
/** The next list entry, null if this is last. */
|
|
Entry next;
|
|
|
|
/** The previous list entry, null if this is first. */
|
|
Entry previous;
|
|
|
|
/**
|
|
* Construct an entry.
|
|
* @param data the list element
|
|
*/
|
|
Entry(Object data)
|
|
{
|
|
this.data = data;
|
|
}
|
|
} // class Entry
|
|
|
|
/**
|
|
* Obtain the Entry at a given position in a list. This method of course
|
|
* takes linear time, but it is intelligent enough to take the shorter of the
|
|
* paths to get to the Entry required. This implies that the first or last
|
|
* entry in the list is obtained in constant time, which is a very desirable
|
|
* property.
|
|
* For speed and flexibility, range checking is not done in this method:
|
|
* Incorrect values will be returned if (n < 0) or (n >= size).
|
|
*
|
|
* @param n the number of the entry to get
|
|
* @return the entry at position n
|
|
*/
|
|
private Entry getEntry(int n)
|
|
{
|
|
Entry e;
|
|
if (n < size / 2)
|
|
{
|
|
e = first;
|
|
// n less than size/2, iterate from start
|
|
while (n-- > 0)
|
|
e = e.next;
|
|
}
|
|
else
|
|
{
|
|
e = last;
|
|
// n greater than size/2, iterate from end
|
|
while (++n < size)
|
|
e = e.previous;
|
|
}
|
|
return e;
|
|
}
|
|
|
|
/**
|
|
* Remove an entry from the list. This will adjust size and deal with
|
|
* `first' and `last' appropriatly.
|
|
*
|
|
* @param e the entry to remove
|
|
*/
|
|
private void removeEntry(Entry e)
|
|
{
|
|
modCount++;
|
|
size--;
|
|
if (size == 0)
|
|
first = last = null;
|
|
else
|
|
{
|
|
if (e == first)
|
|
{
|
|
first = e.next;
|
|
e.next.previous = null;
|
|
}
|
|
else if (e == last)
|
|
{
|
|
last = e.previous;
|
|
e.previous.next = null;
|
|
}
|
|
else
|
|
{
|
|
e.next.previous = e.previous;
|
|
e.previous.next = e.next;
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Checks that the index is in the range of possible elements (inclusive).
|
|
*
|
|
* @param index the index to check
|
|
* @throws IndexOutOfBoundsException if index < 0 || index > size
|
|
*/
|
|
private void checkBoundsInclusive(int index)
|
|
{
|
|
if (index < 0 || index > size)
|
|
throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
|
|
+ size);
|
|
}
|
|
|
|
/**
|
|
* Checks that the index is in the range of existing elements (exclusive).
|
|
*
|
|
* @param index the index to check
|
|
* @throws IndexOutOfBoundsException if index < 0 || index >= size
|
|
*/
|
|
private void checkBoundsExclusive(int index)
|
|
{
|
|
if (index < 0 || index >= size)
|
|
throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
|
|
+ size);
|
|
}
|
|
|
|
/**
|
|
* Create an empty linked list.
|
|
*/
|
|
public LinkedList()
|
|
{
|
|
}
|
|
|
|
/**
|
|
* Create a linked list containing the elements, in order, of a given
|
|
* collection.
|
|
*
|
|
* @param c the collection to populate this list from
|
|
* @throws NullPointerException if c is null
|
|
*/
|
|
public LinkedList(Collection c)
|
|
{
|
|
addAll(c);
|
|
}
|
|
|
|
/**
|
|
* Returns the first element in the list.
|
|
*
|
|
* @return the first list element
|
|
* @throws NoSuchElementException if the list is empty
|
|
*/
|
|
public Object getFirst()
|
|
{
|
|
if (size == 0)
|
|
throw new NoSuchElementException();
|
|
return first.data;
|
|
}
|
|
|
|
/**
|
|
* Returns the last element in the list.
|
|
*
|
|
* @return the last list element
|
|
* @throws NoSuchElementException if the list is empty
|
|
*/
|
|
public Object getLast()
|
|
{
|
|
if (size == 0)
|
|
throw new NoSuchElementException();
|
|
return last.data;
|
|
}
|
|
|
|
/**
|
|
* Remove and return the first element in the list.
|
|
*
|
|
* @return the former first element in the list
|
|
* @throws NoSuchElementException if the list is empty
|
|
*/
|
|
public Object removeFirst()
|
|
{
|
|
if (size == 0)
|
|
throw new NoSuchElementException();
|
|
modCount++;
|
|
size--;
|
|
Object r = first.data;
|
|
|
|
if (first.next != null)
|
|
first.next.previous = null;
|
|
else
|
|
last = null;
|
|
|
|
first = first.next;
|
|
|
|
return r;
|
|
}
|
|
|
|
/**
|
|
* Remove and return the last element in the list.
|
|
*
|
|
* @return the former last element in the list
|
|
* @throws NoSuchElementException if the list is empty
|
|
*/
|
|
public Object removeLast()
|
|
{
|
|
if (size == 0)
|
|
throw new NoSuchElementException();
|
|
modCount++;
|
|
size--;
|
|
Object r = last.data;
|
|
|
|
if (last.previous != null)
|
|
last.previous.next = null;
|
|
else
|
|
first = null;
|
|
|
|
last = last.previous;
|
|
|
|
return r;
|
|
}
|
|
|
|
/**
|
|
* Insert an element at the first of the list.
|
|
*
|
|
* @param o the element to insert
|
|
*/
|
|
public void addFirst(Object o)
|
|
{
|
|
Entry e = new Entry(o);
|
|
|
|
modCount++;
|
|
if (size == 0)
|
|
first = last = e;
|
|
else
|
|
{
|
|
e.next = first;
|
|
first.previous = e;
|
|
first = e;
|
|
}
|
|
size++;
|
|
}
|
|
|
|
/**
|
|
* Insert an element at the last of the list.
|
|
*
|
|
* @param o the element to insert
|
|
*/
|
|
public void addLast(Object o)
|
|
{
|
|
addLastEntry(new Entry(o));
|
|
}
|
|
|
|
/**
|
|
* Inserts an element at the end of the list.
|
|
*
|
|
* @param e the entry to add
|
|
*/
|
|
private void addLastEntry(Entry e)
|
|
{
|
|
modCount++;
|
|
if (size == 0)
|
|
first = last = e;
|
|
else
|
|
{
|
|
e.previous = last;
|
|
last.next = e;
|
|
last = e;
|
|
}
|
|
size++;
|
|
}
|
|
|
|
/**
|
|
* Returns true if the list contains the given object. Comparison is done by
|
|
* <code>o == null ? e = null : o.equals(e)</code>.
|
|
*
|
|
* @param o the element to look for
|
|
* @return true if it is found
|
|
*/
|
|
public boolean contains(Object o)
|
|
{
|
|
Entry e = first;
|
|
while (e != null)
|
|
{
|
|
if (equals(o, e.data))
|
|
return true;
|
|
e = e.next;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Returns the size of the list.
|
|
*
|
|
* @return the list size
|
|
*/
|
|
public int size()
|
|
{
|
|
return size;
|
|
}
|
|
|
|
/**
|
|
* Adds an element to the end of the list.
|
|
*
|
|
* @param e the entry to add
|
|
* @return true, as it always succeeds
|
|
*/
|
|
public boolean add(Object o)
|
|
{
|
|
addLastEntry(new Entry(o));
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* Removes the entry at the lowest index in the list that matches the given
|
|
* object, comparing by <code>o == null ? e = null : o.equals(e)</code>.
|
|
*
|
|
* @param o the object to remove
|
|
* @return true if an instance of the object was removed
|
|
*/
|
|
public boolean remove(Object o)
|
|
{
|
|
Entry e = first;
|
|
while (e != null)
|
|
{
|
|
if (equals(o, e.data))
|
|
{
|
|
removeEntry(e);
|
|
return true;
|
|
}
|
|
e = e.next;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Append the elements of the collection in iteration order to the end of
|
|
* this list. If this list is modified externally (for example, if this
|
|
* list is the collection), behavior is unspecified.
|
|
*
|
|
* @param c the collection to append
|
|
* @return true if the list was modified
|
|
* @throws NullPointerException if c is null
|
|
*/
|
|
public boolean addAll(Collection c)
|
|
{
|
|
return addAll(size, c);
|
|
}
|
|
|
|
/**
|
|
* Insert the elements of the collection in iteration order at the given
|
|
* index of this list. If this list is modified externally (for example,
|
|
* if this list is the collection), behavior is unspecified.
|
|
*
|
|
* @param c the collection to append
|
|
* @return true if the list was modified
|
|
* @throws NullPointerException if c is null
|
|
* @throws IndexOutOfBoundsException if index < 0 || index > size()
|
|
*/
|
|
public boolean addAll(int index, Collection c)
|
|
{
|
|
checkBoundsInclusive(index);
|
|
int csize = c.size();
|
|
|
|
if (csize == 0)
|
|
return false;
|
|
|
|
Iterator itr = c.iterator();
|
|
|
|
// Get the entries just before and after index. If index is at the start
|
|
// of the list, BEFORE is null. If index is at the end of the list, AFTER
|
|
// is null. If the list is empty, both are null.
|
|
Entry after = null;
|
|
Entry before = null;
|
|
if (index != size)
|
|
{
|
|
after = getEntry(index);
|
|
before = after.previous;
|
|
}
|
|
else
|
|
before = last;
|
|
|
|
// Create the first new entry. We do not yet set the link from `before'
|
|
// to the first entry, in order to deal with the case where (c == this).
|
|
// [Actually, we don't have to handle this case to fufill the
|
|
// contract for addAll(), but Sun's implementation appears to.]
|
|
Entry e = new Entry(itr.next());
|
|
e.previous = before;
|
|
Entry prev = e;
|
|
Entry firstNew = e;
|
|
|
|
// Create and link all the remaining entries.
|
|
for (int pos = 1; pos < csize; pos++)
|
|
{
|
|
e = new Entry(itr.next());
|
|
e.previous = prev;
|
|
prev.next = e;
|
|
prev = e;
|
|
}
|
|
|
|
// Link the new chain of entries into the list.
|
|
modCount++;
|
|
size += csize;
|
|
prev.next = after;
|
|
if (after != null)
|
|
after.previous = e;
|
|
else
|
|
last = e;
|
|
|
|
if (before != null)
|
|
before.next = firstNew;
|
|
else
|
|
first = firstNew;
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* Remove all elements from this list.
|
|
*/
|
|
public void clear()
|
|
{
|
|
if (size > 0)
|
|
{
|
|
modCount++;
|
|
first = null;
|
|
last = null;
|
|
size = 0;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Return the element at index.
|
|
*
|
|
* @param index the place to look
|
|
* @return the element at index
|
|
* @throws IndexOutOfBoundsException if index < 0 || index >= size()
|
|
*/
|
|
public Object get(int index)
|
|
{
|
|
checkBoundsExclusive(index);
|
|
return getEntry(index).data;
|
|
}
|
|
|
|
/**
|
|
* Replace the element at the given location in the list.
|
|
*
|
|
* @param index which index to change
|
|
* @param o the new element
|
|
* @return the prior element
|
|
* @throws IndexOutOfBoundsException if index < 0 || index >= size()
|
|
*/
|
|
public Object set(int index, Object o)
|
|
{
|
|
checkBoundsExclusive(index);
|
|
Entry e = getEntry(index);
|
|
Object old = e.data;
|
|
e.data = o;
|
|
return old;
|
|
}
|
|
|
|
/**
|
|
* Inserts an element in the given position in the list.
|
|
*
|
|
* @param index where to insert the element
|
|
* @param o the element to insert
|
|
* @throws IndexOutOfBoundsException if index < 0 || index > size()
|
|
*/
|
|
public void add(int index, Object o)
|
|
{
|
|
checkBoundsInclusive(index);
|
|
Entry e = new Entry(o);
|
|
|
|
if (index < size)
|
|
{
|
|
modCount++;
|
|
Entry after = getEntry(index);
|
|
e.next = after;
|
|
e.previous = after.previous;
|
|
if (after.previous == null)
|
|
first = e;
|
|
else
|
|
after.previous.next = e;
|
|
after.previous = e;
|
|
size++;
|
|
}
|
|
else
|
|
addLastEntry(e);
|
|
}
|
|
|
|
/**
|
|
* Removes the element at the given position from the list.
|
|
*
|
|
* @param index the location of the element to remove
|
|
* @return the removed element
|
|
* @throws IndexOutOfBoundsException if index < 0 || index > size()
|
|
*/
|
|
public Object remove(int index)
|
|
{
|
|
checkBoundsExclusive(index);
|
|
Entry e = getEntry(index);
|
|
removeEntry(e);
|
|
return e.data;
|
|
}
|
|
|
|
/**
|
|
* Returns the first index where the element is located in the list, or -1.
|
|
*
|
|
* @param o the element to look for
|
|
* @return its position, or -1 if not found
|
|
*/
|
|
public int indexOf(Object o)
|
|
{
|
|
int index = 0;
|
|
Entry e = first;
|
|
while (e != null)
|
|
{
|
|
if (equals(o, e.data))
|
|
return index;
|
|
index++;
|
|
e = e.next;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
/**
|
|
* Returns the last index where the element is located in the list, or -1.
|
|
*
|
|
* @param o the element to look for
|
|
* @return its position, or -1 if not found
|
|
*/
|
|
public int lastIndexOf(Object o)
|
|
{
|
|
int index = size - 1;
|
|
Entry e = last;
|
|
while (e != null)
|
|
{
|
|
if (equals(o, e.data))
|
|
return index;
|
|
index--;
|
|
e = e.previous;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
/**
|
|
* Obtain a ListIterator over this list, starting at a given index. The
|
|
* ListIterator returned by this method supports the add, remove and set
|
|
* methods.
|
|
*
|
|
* @param index the index of the element to be returned by the first call to
|
|
* next(), or size() to be initially positioned at the end of the list
|
|
* @throws IndexOutOfBoundsException if index < 0 || index > size()
|
|
*/
|
|
public ListIterator listIterator(int index)
|
|
{
|
|
checkBoundsInclusive(index);
|
|
return new LinkedListItr(index);
|
|
}
|
|
|
|
/**
|
|
* Create a shallow copy of this LinkedList (the elements are not cloned).
|
|
*
|
|
* @return an object of the same class as this object, containing the
|
|
* same elements in the same order
|
|
*/
|
|
public Object clone()
|
|
{
|
|
LinkedList copy = null;
|
|
try
|
|
{
|
|
copy = (LinkedList) super.clone();
|
|
}
|
|
catch (CloneNotSupportedException ex)
|
|
{
|
|
}
|
|
copy.clear();
|
|
copy.addAll(this);
|
|
return copy;
|
|
}
|
|
|
|
/**
|
|
* Returns an array which contains the elements of the list in order.
|
|
*
|
|
* @return an array containing the list elements
|
|
*/
|
|
public Object[] toArray()
|
|
{
|
|
Object[] array = new Object[size];
|
|
Entry e = first;
|
|
for (int i = 0; i < size; i++)
|
|
{
|
|
array[i] = e.data;
|
|
e = e.next;
|
|
}
|
|
return array;
|
|
}
|
|
|
|
/**
|
|
* Returns an Array whose component type is the runtime component type of
|
|
* the passed-in Array. The returned Array is populated with all of the
|
|
* elements in this LinkedList. If the passed-in Array is not large enough
|
|
* to store all of the elements in this List, a new Array will be created
|
|
* and returned; if the passed-in Array is <i>larger</i> than the size
|
|
* of this List, then size() index will be set to null.
|
|
*
|
|
* @param a the passed-in Array
|
|
* @return an array representation of this list
|
|
* @throws ArrayStoreException if the runtime type of a does not allow
|
|
* an element in this list
|
|
* @throws NullPointerException if a is null
|
|
*/
|
|
public Object[] toArray(Object[] a)
|
|
{
|
|
if (a.length < size)
|
|
a = (Object[]) Array.newInstance(a.getClass().getComponentType(), size);
|
|
else if (a.length > size)
|
|
a[size] = null;
|
|
Entry e = first;
|
|
for (int i = 0; i < size; i++)
|
|
{
|
|
a[i] = e.data;
|
|
e = e.next;
|
|
}
|
|
return a;
|
|
}
|
|
|
|
/**
|
|
* Serializes this object to the given stream.
|
|
*
|
|
* @param s the stream to write to
|
|
* @throws IOException if the underlying stream fails
|
|
* @serialData the size of the list (int), followed by all the elements
|
|
* (Object) in proper order
|
|
*/
|
|
private void writeObject(ObjectOutputStream s) throws IOException
|
|
{
|
|
s.defaultWriteObject();
|
|
s.writeInt(size);
|
|
Entry e = first;
|
|
while (e != null)
|
|
{
|
|
s.writeObject(e.data);
|
|
e = e.next;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Deserializes this object from the given stream.
|
|
*
|
|
* @param s the stream to read from
|
|
* @throws ClassNotFoundException if the underlying stream fails
|
|
* @throws IOException if the underlying stream fails
|
|
* @serialData the size of the list (int), followed by all the elements
|
|
* (Object) in proper order
|
|
*/
|
|
private void readObject(ObjectInputStream s)
|
|
throws IOException, ClassNotFoundException
|
|
{
|
|
s.defaultReadObject();
|
|
int i = s.readInt();
|
|
while (--i >= 0)
|
|
addLastEntry(new Entry(s.readObject()));
|
|
}
|
|
|
|
/**
|
|
* A ListIterator over the list. This class keeps track of its
|
|
* position in the list and the two list entries it is between.
|
|
*
|
|
* @author Original author unknown
|
|
* @author Eric Blake <ebb9@email.byu.edu>
|
|
*/
|
|
private final class LinkedListItr implements ListIterator
|
|
{
|
|
/** Number of modifications we know about. */
|
|
private int knownMod = modCount;
|
|
|
|
/** Entry that will be returned by next(). */
|
|
private Entry next;
|
|
|
|
/** Entry that will be returned by previous(). */
|
|
private Entry previous;
|
|
|
|
/** Entry that will be affected by remove() or set(). */
|
|
private Entry lastReturned;
|
|
|
|
/** Index of `next'. */
|
|
private int position;
|
|
|
|
/**
|
|
* Initialize the iterator.
|
|
*
|
|
* @param index the initial index
|
|
*/
|
|
LinkedListItr(int index)
|
|
{
|
|
if (index == size)
|
|
{
|
|
next = null;
|
|
previous = last;
|
|
}
|
|
else
|
|
{
|
|
next = getEntry(index);
|
|
previous = next.previous;
|
|
}
|
|
position = index;
|
|
}
|
|
|
|
/**
|
|
* Checks for iterator consistency.
|
|
*
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
private void checkMod()
|
|
{
|
|
if (knownMod != modCount)
|
|
throw new ConcurrentModificationException();
|
|
}
|
|
|
|
/**
|
|
* Returns the index of the next element.
|
|
*
|
|
* @return the next index
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public int nextIndex()
|
|
{
|
|
checkMod();
|
|
return position;
|
|
}
|
|
|
|
/**
|
|
* Returns the index of the previous element.
|
|
*
|
|
* @return the previous index
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public int previousIndex()
|
|
{
|
|
checkMod();
|
|
return position - 1;
|
|
}
|
|
|
|
/**
|
|
* Returns true if more elements exist via next.
|
|
*
|
|
* @return true if next will succeed
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public boolean hasNext()
|
|
{
|
|
checkMod();
|
|
return (next != null);
|
|
}
|
|
|
|
/**
|
|
* Returns true if more elements exist via previous.
|
|
*
|
|
* @return true if previous will succeed
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public boolean hasPrevious()
|
|
{
|
|
checkMod();
|
|
return (previous != null);
|
|
}
|
|
|
|
/**
|
|
* Returns the next element.
|
|
*
|
|
* @return the next element
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
* @throws NoSuchElementException if there is no next
|
|
*/
|
|
public Object next()
|
|
{
|
|
checkMod();
|
|
if (next == null)
|
|
throw new NoSuchElementException();
|
|
position++;
|
|
lastReturned = previous = next;
|
|
next = lastReturned.next;
|
|
return lastReturned.data;
|
|
}
|
|
|
|
/**
|
|
* Returns the previous element.
|
|
*
|
|
* @return the previous element
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
* @throws NoSuchElementException if there is no previous
|
|
*/
|
|
public Object previous()
|
|
{
|
|
checkMod();
|
|
if (previous == null)
|
|
throw new NoSuchElementException();
|
|
position--;
|
|
lastReturned = next = previous;
|
|
previous = lastReturned.previous;
|
|
return lastReturned.data;
|
|
}
|
|
|
|
/**
|
|
* Remove the most recently returned element from the list.
|
|
*
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
* @throws IllegalStateException if there was no last element
|
|
*/
|
|
public void remove()
|
|
{
|
|
checkMod();
|
|
if (lastReturned == null)
|
|
throw new IllegalStateException();
|
|
|
|
// Adjust the position to before the removed element, if the element
|
|
// being removed is behind the cursor.
|
|
if (lastReturned == previous)
|
|
position--;
|
|
|
|
next = lastReturned.next;
|
|
previous = lastReturned.previous;
|
|
removeEntry(lastReturned);
|
|
knownMod++;
|
|
|
|
lastReturned = null;
|
|
}
|
|
|
|
/**
|
|
* Adds an element between the previous and next, and advance to the next.
|
|
*
|
|
* @param o the element to add
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public void add(Object o)
|
|
{
|
|
checkMod();
|
|
modCount++;
|
|
knownMod++;
|
|
size++;
|
|
position++;
|
|
Entry e = new Entry(o);
|
|
e.previous = previous;
|
|
e.next = next;
|
|
|
|
if (previous != null)
|
|
previous.next = e;
|
|
else
|
|
first = e;
|
|
|
|
if (next != null)
|
|
next.previous = e;
|
|
else
|
|
last = e;
|
|
|
|
previous = e;
|
|
lastReturned = null;
|
|
}
|
|
|
|
/**
|
|
* Changes the contents of the element most recently returned.
|
|
*
|
|
* @param o the new element
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
* @throws IllegalStateException if there was no last element
|
|
*/
|
|
public void set(Object o)
|
|
{
|
|
checkMod();
|
|
if (lastReturned == null)
|
|
throw new IllegalStateException();
|
|
lastReturned.data = o;
|
|
}
|
|
} // class LinkedListItr
|
|
}
|