--- jsr166/src/main/java/util/LinkedList.java 2003/11/17 08:05:59 1.12
+++ jsr166/src/main/java/util/LinkedList.java 2006/01/10 21:32:09 1.43
@@ -1,11 +1,12 @@
/*
* %W% %E%
*
- * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
+ * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
+import java.util.*; // for javadoc (till 6280605 is fixed)
/**
* Linked list implementation of the List interface. Implements all
@@ -14,40 +15,41 @@ package java.util;
* the LinkedList class provides uniformly named methods to
* get, remove and insert an element at the
* beginning and end of the list. These operations allow linked lists to be
- * used as a stack, queue, or double-ended queue (deque).
+ * used as a stack, {@linkplain Queue queue}, or {@linkplain Deque
+ * double-ended queue}.
*
- * The class implements the Queue interface, providing
+ * The class implements the Deque interface, providing
* first-in-first-out queue operations for add,
- * poll, etc. Other stack and deque operations could be
- * easily recast in terms of the standard list operations. They're
- * included here primarily for convenience, though they may run
- * slightly faster than the equivalent List operations.
+ * poll, along with other stack and deque operations.
*
* All of the operations perform as could be expected for a doubly-linked
* list. Operations that index into the list will traverse the list from
* the beginning or the end, whichever is closer to the specified index.
*
- * Note that this implementation is not synchronized. If multiple
- * threads access a list concurrently, and at least one of the threads
- * modifies the list structurally, it must be synchronized
- * externally. (A structural modification is any operation that adds or
- * deletes one or more elements; merely setting the value of an element is not
- * a structural modification.) This is typically accomplished by
- * synchronizing on some object that naturally encapsulates the list. If no
- * such object exists, the list should be "wrapped" using the
- * Collections.synchronizedList method. This is best done at creation time,
- * to prevent accidental unsynchronized access to the list:
- * List list = Collections.synchronizedList(new LinkedList(...));
- *
+ *
Note that this implementation is not synchronized.
+ * If multiple threads access a linked list concurrently, and at least
+ * one of the threads modifies the list structurally, it must be
+ * synchronized externally. (A structural modification is any operation
+ * that adds or deletes one or more elements; merely setting the value of
+ * an element is not a structural modification.) This is typically
+ * accomplished by synchronizing on some object that naturally
+ * encapsulates the list.
*
- * The iterators returned by the this class's iterator and
+ * If no such object exists, the list should be "wrapped" using the
+ * {@link Collections#synchronizedList Collections.synchronizedList}
+ * method. This is best done at creation time, to prevent accidental
+ * unsynchronized access to the list:
+ * List list = Collections.synchronizedList(new LinkedList(...));
+ *
+ * The iterators returned by this class's iterator and
* listIterator methods are fail-fast: if the list is
- * structurally modified at any time after the iterator is created, in any way
- * except through the Iterator's own remove or add methods,
- * the iterator will throw a ConcurrentModificationException. Thus,
- * in the face of concurrent modification, the iterator fails quickly and
- * cleanly, rather than risking arbitrary, non-deterministic behavior at an
- * undetermined time in the future.
+ * structurally modified at any time after the iterator is created, in
+ * any way except through the Iterator's own remove or
+ * add methods, the iterator will throw a {@link
+ * ConcurrentModificationException}. Thus, in the face of concurrent
+ * modification, the iterator fails quickly and cleanly, rather than
+ * risking arbitrary, non-deterministic behavior at an undetermined
+ * time in the future.
*
*
Note that the fail-fast behavior of an iterator cannot be guaranteed
* as it is, generally speaking, impossible to make any hard guarantees in the
@@ -55,25 +57,24 @@ package java.util;
* throw ConcurrentModificationException on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: the fail-fast behavior of iterators
- * should be used only to detect bugs.
+ * should be used only to detect bugs.
*
- * This class is a member of the
+ *
This class is a member of the
*
* Java Collections Framework.
*
* @author Josh Bloch
* @version %I%, %G%
- * @see List
- * @see ArrayList
- * @see Vector
- * @see Collections#synchronizedList(List)
+ * @see List
+ * @see ArrayList
+ * @see Vector
* @since 1.2
* @param the type of elements held in this collection
*/
public class LinkedList
extends AbstractSequentialList
- implements List, Queue, Cloneable, java.io.Serializable
+ implements List, Deque, Cloneable, java.io.Serializable
{
private transient Entry header = new Entry(null, null, null);
private transient int size = 0;
@@ -90,91 +91,88 @@ public class LinkedList
* collection, in the order they are returned by the collection's
* iterator.
*
- * @param c the collection whose elements are to be placed into this list.
- * @throws NullPointerException if the specified collection is null.
+ * @param c the collection whose elements are to be placed into this list
+ * @throws NullPointerException if the specified collection is null
*/
public LinkedList(Collection extends E> c) {
- this();
- addAll(c);
- }
+ this();
+ addAll(c);
+ }
/**
* Returns the first element in this list.
*
- * @return the first element in this list.
- * @throws NoSuchElementException if this list is empty.
+ * @return the first element in this list
+ * @throws NoSuchElementException if this list is empty
*/
public E getFirst() {
- if (size==0)
- throw new NoSuchElementException();
+ if (size==0)
+ throw new NoSuchElementException();
- return header.next.element;
+ return header.next.element;
}
/**
* Returns the last element in this list.
*
- * @return the last element in this list.
- * @throws NoSuchElementException if this list is empty.
+ * @return the last element in this list
+ * @throws NoSuchElementException if this list is empty
*/
public E getLast() {
- if (size==0)
- throw new NoSuchElementException();
+ if (size==0)
+ throw new NoSuchElementException();
- return header.previous.element;
+ return header.previous.element;
}
/**
* Removes and returns the first element from this list.
*
- * @return the first element from this list.
- * @throws NoSuchElementException if this list is empty.
+ * @return the first element from this list
+ * @throws NoSuchElementException if this list is empty
*/
public E removeFirst() {
- E first = header.next.element;
- remove(header.next);
- return first;
+ return remove(header.next);
}
/**
* Removes and returns the last element from this list.
*
- * @return the last element from this list.
- * @throws NoSuchElementException if this list is empty.
+ * @return the last element from this list
+ * @throws NoSuchElementException if this list is empty
*/
public E removeLast() {
- E last = header.previous.element;
- remove(header.previous);
- return last;
+ return remove(header.previous);
}
/**
- * Inserts the given element at the beginning of this list.
+ * Inserts the specified element at the beginning of this list.
*
- * @param o the element to be inserted at the beginning of this list.
+ * @param e the element to add
*/
- public void addFirst(E o) {
- addBefore(o, header.next);
+ public void addFirst(E e) {
+ addBefore(e, header.next);
}
/**
- * Appends the given element to the end of this list. (Identical in
- * function to the add method; included only for consistency.)
+ * Appends the specified element to the end of this list.
*
- * @param o the element to be inserted at the end of this list.
+ * This method is equivalent to {@link #add}.
+ *
+ * @param e the element to add
*/
- public void addLast(E o) {
- addBefore(o, header);
+ public void addLast(E e) {
+ addBefore(e, header);
}
/**
* Returns true if this list contains the specified element.
* More formally, returns true if and only if this list contains
- * at least one element e such that (o==null ? e==null
- * : o.equals(e)).
+ * at least one element e such that
+ * (o==null ? e==null : o.equals(e)).
*
- * @param o element whose presence in this list is to be tested.
- * @return true if this list contains the specified element.
+ * @param o element whose presence in this list is to be tested
+ * @return true if this list contains the specified element
*/
public boolean contains(Object o) {
return indexOf(o) != -1;
@@ -183,33 +181,37 @@ public class LinkedList
/**
* Returns the number of elements in this list.
*
- * @return the number of elements in this list.
+ * @return the number of elements in this list
*/
public int size() {
- return size;
+ return size;
}
/**
* Appends the specified element to the end of this list.
*
- * @param o element to be appended to this list.
- * @return true (as per the general contract of
- * Collection.add).
+ * This method is equivalent to {@link #addLast}.
+ *
+ * @param e element to be appended to this list
+ * @return true (as specified by {@link Collection#add})
*/
- public boolean add(E o) {
- addBefore(o, header);
+ public boolean add(E e) {
+ addBefore(e, header);
return true;
}
/**
- * Removes the first occurrence of the specified element in this list. If
- * the list does not contain the element, it is unchanged. More formally,
- * removes the element with the lowest index i such that
- * (o==null ? get(i)==null : o.equals(get(i))) (if such an
- * element exists).
+ * Removes the first occurrence of the specified element from this list,
+ * if it is present. If this list does not contain the element, it is
+ * unchanged. More formally, removes the element with the lowest index
+ * i such that
+ * (o==null ? get(i)==null : o.equals(get(i)))
+ * (if such an element exists). Returns true if this list
+ * contained the specified element (or equivalently, if this list
+ * changed as a result of the call).
*
- * @param o element to be removed from this list, if present.
- * @return true if the list contained the specified element.
+ * @param o element to be removed from this list, if present
+ * @return true if this list contained the specified element
*/
public boolean remove(Object o) {
if (o==null) {
@@ -235,12 +237,12 @@ public class LinkedList
* this list, in the order that they are returned by the specified
* collection's iterator. The behavior of this operation is undefined if
* the specified collection is modified while the operation is in
- * progress. (This implies that the behavior of this call is undefined if
- * the specified Collection is this list, and this list is nonempty.)
+ * progress. (Note that this will occur if the specified collection is
+ * this list, and it's nonempty.)
*
- * @param c the elements to be inserted into this list.
- * @return true if this list changed as a result of the call.
- * @throws NullPointerException if the specified collection is null.
+ * @param c collection containing elements to be added to this list
+ * @return true if this list changed as a result of the call
+ * @throws NullPointerException if the specified collection is null
*/
public boolean addAll(Collection extends E> c) {
return addAll(size, c);
@@ -254,13 +256,12 @@ public class LinkedList
* in the list in the order that they are returned by the
* specified collection's iterator.
*
- * @param index index at which to insert first element
- * from the specified collection.
- * @param c elements to be inserted into this list.
- * @return true if this list changed as a result of the call.
- * @throws IndexOutOfBoundsException if the specified index is out of
- * range (index < 0 || index > size()).
- * @throws NullPointerException if the specified collection is null.
+ * @param index index at which to insert the first element
+ * from the specified collection
+ * @param c collection containing elements to be added to this list
+ * @return true if this list changed as a result of the call
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @throws NullPointerException if the specified collection is null
*/
public boolean addAll(int index, Collection extends E> c) {
if (index < 0 || index > size)
@@ -270,11 +271,11 @@ public class LinkedList
int numNew = a.length;
if (numNew==0)
return false;
- modCount++;
+ modCount++;
Entry successor = (index==size ? header : entry(index));
Entry predecessor = successor.previous;
- for (int i=0; i e = new Entry((E)a[i], successor, predecessor);
predecessor.next = e;
predecessor = e;
@@ -289,9 +290,16 @@ public class LinkedList
* Removes all of the elements from this list.
*/
public void clear() {
- modCount++;
+ Entry e = header.next;
+ while (e != header) {
+ Entry next = e.next;
+ e.next = e.previous = null;
+ e.element = null;
+ e = next;
+ }
header.next = header.previous = header;
size = 0;
+ modCount++;
}
@@ -300,11 +308,9 @@ public class LinkedList
/**
* Returns the element at the specified position in this list.
*
- * @param index index of element to return.
- * @return the element at the specified position in this list.
- *
- * @throws IndexOutOfBoundsException if the specified index is is out of
- * range (index < 0 || index >= size()).
+ * @param index index of the element to return
+ * @return the element at the specified position in this list
+ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E get(int index) {
return entry(index).element;
@@ -314,11 +320,10 @@ public class LinkedList
* Replaces the element at the specified position in this list with the
* specified element.
*
- * @param index index of element to replace.
- * @param element element to be stored at the specified position.
- * @return the element previously at the specified position.
- * @throws IndexOutOfBoundsException if the specified index is out of
- * range (index < 0 || index >= size()).
+ * @param index index of the element to replace
+ * @param element element to be stored at the specified position
+ * @return the element previously at the specified position
+ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E set(int index, E element) {
Entry e = entry(index);
@@ -332,11 +337,9 @@ public class LinkedList
* Shifts the element currently at that position (if any) and any
* subsequent elements to the right (adds one to their indices).
*
- * @param index index at which the specified element is to be inserted.
- * @param element element to be inserted.
- *
- * @throws IndexOutOfBoundsException if the specified index is out of
- * range (index < 0 || index > size()).
+ * @param index index at which the specified element is to be inserted
+ * @param element element to be inserted
+ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
public void add(int index, E element) {
addBefore(element, (index==size ? header : entry(index)));
@@ -347,20 +350,16 @@ public class LinkedList
* subsequent elements to the left (subtracts one from their indices).
* Returns the element that was removed from the list.
*
- * @param index the index of the element to removed.
- * @return the element previously at the specified position.
- *
- * @throws IndexOutOfBoundsException if the specified index is out of
- * range (index < 0 || index >= size()).
+ * @param index the index of the element to be removed
+ * @return the element previously at the specified position
+ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E remove(int index) {
- Entry e = entry(index);
- remove(e);
- return e.element;
+ return remove(entry(index));
}
/**
- * Return the indexed entry.
+ * Returns the indexed entry.
*/
private Entry entry(int index) {
if (index < 0 || index >= size)
@@ -381,16 +380,15 @@ public class LinkedList
// Search Operations
/**
- * Returns the index in this list of the first occurrence of the
- * specified element, or -1 if the List does not contain this
- * element. More formally, returns the lowest index i such that
- * (o==null ? get(i)==null : o.equals(get(i))), or -1 if
- * there is no such index.
- *
- * @param o element to search for.
- * @return the index in this list of the first occurrence of the
- * specified element, or -1 if the list does not contain this
- * element.
+ * Returns the index of the first occurrence of the specified element
+ * in this list, or -1 if this list does not contain the element.
+ * More formally, returns the lowest index i such that
+ * (o==null ? get(i)==null : o.equals(get(i))),
+ * or -1 if there is no such index.
+ *
+ * @param o element to search for
+ * @return the index of the first occurrence of the specified element in
+ * this list, or -1 if this list does not contain the element
*/
public int indexOf(Object o) {
int index = 0;
@@ -411,16 +409,15 @@ public class LinkedList
}
/**
- * Returns the index in this list of the last occurrence of the
- * specified element, or -1 if the list does not contain this
- * element. More formally, returns the highest index i such that
- * (o==null ? get(i)==null : o.equals(get(i))), or -1 if
- * there is no such index.
- *
- * @param o element to search for.
- * @return the index in this list of the last occurrence of the
- * specified element, or -1 if the list does not contain this
- * element.
+ * Returns the index of the last occurrence of the specified element
+ * in this list, or -1 if this list does not contain the element.
+ * More formally, returns the highest index i such that
+ * (o==null ? get(i)==null : o.equals(get(i))),
+ * or -1 if there is no such index.
+ *
+ * @param o element to search for
+ * @return the index of the last occurrence of the specified element in
+ * this list, or -1 if this list does not contain the element
*/
public int lastIndexOf(Object o) {
int index = size;
@@ -444,7 +441,7 @@ public class LinkedList
/**
* Retrieves, but does not remove, the head (first element) of this list.
- * @return the head of this queue, or null if this queue is empty.
+ * @return the head of this list, or null if this list is empty
* @since 1.5
*/
public E peek() {
@@ -455,8 +452,8 @@ public class LinkedList
/**
* Retrieves, but does not remove, the head (first element) of this list.
- * @return the head of this queue.
- * @throws NoSuchElementException if this queue is empty.
+ * @return the head of this list
+ * @throws NoSuchElementException if this list is empty
* @since 1.5
*/
public E element() {
@@ -464,8 +461,8 @@ public class LinkedList
}
/**
- * Retrieves and removes the head (first element) of this list.
- * @return the head of this queue, or null if this queue is empty.
+ * Retrieves and removes the head (first element) of this list
+ * @return the head of this list, or null if this list is empty
* @since 1.5
*/
public E poll() {
@@ -476,8 +473,9 @@ public class LinkedList
/**
* Retrieves and removes the head (first element) of this list.
- * @return the head of this queue.
- * @throws NoSuchElementException if this queue is empty.
+ *
+ * @return the head of this list
+ * @throws NoSuchElementException if this list is empty
* @since 1.5
*/
public E remove() {
@@ -487,13 +485,162 @@ public class LinkedList
/**
* Adds the specified element as the tail (last element) of this list.
*
- * @param o the element to add.
- * @return true (as per the general contract of
- * Queue.offer)
+ * @param e the element to add
+ * @return true (as specified by {@link Queue#offer})
* @since 1.5
*/
- public boolean offer(E o) {
- return add(o);
+ public boolean offer(E e) {
+ return add(e);
+ }
+
+ // Deque operations
+ /**
+ * Inserts the specified element at the front of this list.
+ *
+ * @param e the element to insert
+ * @return true (as specified by {@link Deque#offerFirst})
+ * @since 1.6
+ */
+ public boolean offerFirst(E e) {
+ addFirst(e);
+ return true;
+ }
+
+ /**
+ * Inserts the specified element at the end of this list.
+ *
+ * @param e the element to insert
+ * @return true (as specified by {@link Deque#offerLast})
+ * @since 1.6
+ */
+ public boolean offerLast(E e) {
+ addLast(e);
+ return true;
+ }
+
+ /**
+ * Retrieves, but does not remove, the first element of this list,
+ * or returns null if this list is empty.
+ *
+ * @return the first element of this list, or null
+ * if this list is empty
+ * @since 1.6
+ */
+ public E peekFirst() {
+ if (size==0)
+ return null;
+ return getFirst();
+ }
+
+ /**
+ * Retrieves, but does not remove, the last element of this list,
+ * or returns null if this list is empty.
+ *
+ * @return the last element of this list, or null
+ * if this list is empty
+ * @since 1.6
+ */
+ public E peekLast() {
+ if (size==0)
+ return null;
+ return getLast();
+ }
+
+ /**
+ * Retrieves and removes the first element of this list,
+ * or returns null if this list is empty.
+ *
+ * @return the first element of this list, or null if
+ * this list is empty
+ * @since 1.6
+ */
+ public E pollFirst() {
+ if (size==0)
+ return null;
+ return removeFirst();
+ }
+
+ /**
+ * Retrieves and removes the last element of this list,
+ * or returns null if this list is empty.
+ *
+ * @return the last element of this list, or null if
+ * this list is empty
+ * @since 1.6
+ */
+ public E pollLast() {
+ if (size==0)
+ return null;
+ return removeLast();
+ }
+
+ /**
+ * Pushes an element onto the stack represented by this list. In other
+ * words, inserts the element at the front of this list.
+ *
+ * This method is equivalent to {@link #addFirst}.
+ *
+ * @param e the element to push
+ * @since 1.6
+ */
+ public void push(E e) {
+ addFirst(e);
+ }
+
+ /**
+ * Pops an element from the stack represented by this list. In other
+ * words, removes and returns the first element of this list.
+ *
+ *
This method is equivalent to {@link #removeFirst()}.
+ *
+ * @return the element at the front of this list (which is the top
+ * of the stack represented by this list)
+ * @throws NoSuchElementException if this list is empty
+ * @since 1.6
+ */
+ public E pop() {
+ return removeFirst();
+ }
+
+ /**
+ * Removes the first occurrence of the specified element in this
+ * list (when traversing the list from head to tail). If the list
+ * does not contain the element, it is unchanged.
+ *
+ * @param o element to be removed from this list, if present
+ * @return true if the list contained the specified element
+ * @since 1.6
+ */
+ public boolean removeFirstOccurrence(Object o) {
+ return remove(o);
+ }
+
+ /**
+ * Removes the last occurrence of the specified element in this
+ * list (when traversing the list from head to tail). If the list
+ * does not contain the element, it is unchanged.
+ *
+ * @param o element to be removed from this list, if present
+ * @return true if the list contained the specified element
+ * @since 1.6
+ */
+ public boolean removeLastOccurrence(Object o) {
+ if (o==null) {
+ for (Entry e = header.previous; e != header; e = e.previous) {
+ if (e.element==null) {
+ remove(e);
+ return true;
+ }
+ }
+ } else {
+ for (Entry e = header.previous; e != header; e = e.previous) {
+ if (o.equals(e.element)) {
+ remove(e);
+ return true;
+ }
+ }
+ }
+ return false;
}
/**
@@ -510,156 +657,181 @@ public class LinkedList
* than risking arbitrary, non-deterministic behavior at an undetermined
* time in the future.
*
- * @param index index of first element to be returned from the
- * list-iterator (by a call to next).
+ * @param index index of the first element to be returned from the
+ * list-iterator (by a call to next)
* @return a ListIterator of the elements in this list (in proper
- * sequence), starting at the specified position in the list.
- * @throws IndexOutOfBoundsException if index is out of range
- * (index < 0 || index > size()).
+ * sequence), starting at the specified position in the list
+ * @throws IndexOutOfBoundsException {@inheritDoc}
* @see List#listIterator(int)
*/
public ListIterator listIterator(int index) {
- return new ListItr(index);
+ return new ListItr(index);
}
private class ListItr implements ListIterator {
- private Entry lastReturned = header;
- private Entry next;
- private int nextIndex;
- private int expectedModCount = modCount;
-
- ListItr(int index) {
- if (index < 0 || index > size)
- throw new IndexOutOfBoundsException("Index: "+index+
- ", Size: "+size);
- if (index < (size >> 1)) {
- next = header.next;
- for (nextIndex=0; nextIndexindex; nextIndex--)
- next = next.previous;
- }
- }
-
- public boolean hasNext() {
- return nextIndex != size;
- }
+ private Entry lastReturned = header;
+ private Entry next;
+ private int nextIndex;
+ private int expectedModCount = modCount;
+
+ ListItr(int index) {
+ if (index < 0 || index > size)
+ throw new IndexOutOfBoundsException("Index: "+index+
+ ", Size: "+size);
+ if (index < (size >> 1)) {
+ next = header.next;
+ for (nextIndex=0; nextIndexindex; nextIndex--)
+ next = next.previous;
+ }
+ }
+
+ public boolean hasNext() {
+ return nextIndex != size;
+ }
+
+ public E next() {
+ checkForComodification();
+ if (nextIndex == size)
+ throw new NoSuchElementException();
+
+ lastReturned = next;
+ next = next.next;
+ nextIndex++;
+ return lastReturned.element;
+ }
+
+ public boolean hasPrevious() {
+ return nextIndex != 0;
+ }
+
+ public E previous() {
+ if (nextIndex == 0)
+ throw new NoSuchElementException();
+
+ lastReturned = next = next.previous;
+ nextIndex--;
+ checkForComodification();
+ return lastReturned.element;
+ }
+
+ public int nextIndex() {
+ return nextIndex;
+ }
+
+ public int previousIndex() {
+ return nextIndex-1;
+ }
- public E next() {
- checkForComodification();
- if (nextIndex == size)
- throw new NoSuchElementException();
-
- lastReturned = next;
- next = next.next;
- nextIndex++;
- return lastReturned.element;
- }
-
- public boolean hasPrevious() {
- return nextIndex != 0;
- }
-
- public E previous() {
- if (nextIndex == 0)
- throw new NoSuchElementException();
-
- lastReturned = next = next.previous;
- nextIndex--;
- checkForComodification();
- return lastReturned.element;
- }
-
- public int nextIndex() {
- return nextIndex;
- }
-
- public int previousIndex() {
- return nextIndex-1;
- }
-
- public void remove() {
+ public void remove() {
checkForComodification();
+ Entry lastNext = lastReturned.next;
try {
LinkedList.this.remove(lastReturned);
} catch (NoSuchElementException e) {
throw new IllegalStateException();
}
- if (next==lastReturned)
- next = lastReturned.next;
+ if (next==lastReturned)
+ next = lastNext;
else
- nextIndex--;
- lastReturned = header;
- expectedModCount++;
- }
-
- public void set(E o) {
- if (lastReturned == header)
- throw new IllegalStateException();
- checkForComodification();
- lastReturned.element = o;
- }
-
- public void add(E o) {
- checkForComodification();
- lastReturned = header;
- addBefore(o, next);
- nextIndex++;
- expectedModCount++;
- }
-
- final void checkForComodification() {
- if (modCount != expectedModCount)
- throw new ConcurrentModificationException();
- }
+ nextIndex--;
+ lastReturned = header;
+ expectedModCount++;
+ }
+
+ public void set(E e) {
+ if (lastReturned == header)
+ throw new IllegalStateException();
+ checkForComodification();
+ lastReturned.element = e;
+ }
+
+ public void add(E e) {
+ checkForComodification();
+ lastReturned = header;
+ addBefore(e, next);
+ nextIndex++;
+ expectedModCount++;
+ }
+
+ final void checkForComodification() {
+ if (modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+ }
}
private static class Entry {
- E element;
- Entry next;
- Entry previous;
-
- Entry(E element, Entry next, Entry previous) {
- this.element = element;
- this.next = next;
- this.previous = previous;
- }
+ E element;
+ Entry next;
+ Entry previous;
+
+ Entry(E element, Entry next, Entry previous) {
+ this.element = element;
+ this.next = next;
+ this.previous = previous;
+ }
+ }
+
+ private Entry addBefore(E e, Entry entry) {
+ Entry newEntry = new Entry(e, entry, entry.previous);
+ newEntry.previous.next = newEntry;
+ newEntry.next.previous = newEntry;
+ size++;
+ modCount++;
+ return newEntry;
+ }
+
+ private E remove(Entry e) {
+ if (e == header)
+ throw new NoSuchElementException();
+
+ E result = e.element;
+ e.previous.next = e.next;
+ e.next.previous = e.previous;
+ e.next = e.previous = null;
+ e.element = null;
+ size--;
+ modCount++;
+ return result;
+ }
+
+ /**
+ * @since 1.6
+ */
+ public Iterator descendingIterator() {
+ return new DescendingIterator();
}
- private Entry addBefore(E o, Entry e) {
- Entry newEntry = new Entry(o, e, e.previous);
- newEntry.previous.next = newEntry;
- newEntry.next.previous = newEntry;
- size++;
- modCount++;
- return newEntry;
- }
-
- private void remove(Entry e) {
- if (e == header)
- throw new NoSuchElementException();
-
- e.previous.next = e.next;
- e.next.previous = e.previous;
- size--;
- modCount++;
+ /** Adapter to provide descending iterators via ListItr.previous */
+ private class DescendingIterator implements Iterator {
+ final ListItr itr = new ListItr(size());
+ public boolean hasNext() {
+ return itr.hasPrevious();
+ }
+ public E next() {
+ return itr.previous();
+ }
+ public void remove() {
+ itr.remove();
+ }
}
/**
* Returns a shallow copy of this LinkedList. (The elements
* themselves are not cloned.)
*
- * @return a shallow copy of this LinkedList instance.
+ * @return a shallow copy of this LinkedList instance
*/
public Object clone() {
LinkedList clone = null;
- try {
- clone = (LinkedList) super.clone();
- } catch (CloneNotSupportedException e) {
- throw new InternalError();
- }
+ try {
+ clone = (LinkedList) super.clone();
+ } catch (CloneNotSupportedException e) {
+ throw new InternalError();
+ }
// Put clone into "virgin" state
clone.header = new Entry(null, null, null);
@@ -676,47 +848,70 @@ public class LinkedList
/**
* Returns an array containing all of the elements in this list
- * in the correct order.
+ * in proper sequence (from first to last element).
+ *
+ * The returned array will be "safe" in that no references to it are
+ * maintained by this list. (In other words, this method must allocate
+ * a new array). The caller is thus free to modify the returned array.
+ *
+ *
This method acts as bridge between array-based and collection-based
+ * APIs.
*
* @return an array containing all of the elements in this list
- * in the correct order.
+ * in proper sequence
*/
public Object[] toArray() {
- Object[] result = new Object[size];
+ Object[] result = new Object[size];
int i = 0;
for (Entry e = header.next; e != header; e = e.next)
result[i++] = e.element;
- return result;
+ return result;
}
/**
* Returns an array containing all of the elements in this list in
- * the correct order; the runtime type of the returned array is that of
- * the specified array. If the list fits in the specified array, it
- * is returned therein. Otherwise, a new array is allocated with the
- * runtime type of the specified array and the size of this list.
- *
- * If the list fits in the specified array with room to spare
- * (i.e., the array has more elements than the list),
- * the element in the array immediately following the end of the
- * collection is set to null. This is useful in determining the length
- * of the list only if the caller knows that the list
- * does not contain any null elements.
+ * proper sequence (from first to last element); the runtime type of
+ * the returned array is that of the specified array. If the list fits
+ * in the specified array, it is returned therein. Otherwise, a new
+ * array is allocated with the runtime type of the specified array and
+ * the size of this list.
+ *
+ *
If the list fits in the specified array with room to spare (i.e.,
+ * the array has more elements than the list), the element in the array
+ * immediately following the end of the list is set to null.
+ * (This is useful in determining the length of the list only if
+ * the caller knows that the list does not contain any null elements.)
+ *
+ *
Like the {@link #toArray()} method, this method acts as bridge between
+ * array-based and collection-based APIs. Further, this method allows
+ * precise control over the runtime type of the output array, and may,
+ * under certain circumstances, be used to save allocation costs.
+ *
+ *
Suppose x is a list known to contain only strings.
+ * The following code can be used to dump the list into a newly
+ * allocated array of String:
+ *
+ *
+ * String[] y = x.toArray(new String[0]);
+ *
+ * Note that toArray(new Object[0]) is identical in function to
+ * toArray().
*
* @param a the array into which the elements of the list are to
* be stored, if it is big enough; otherwise, a new array of the
* same runtime type is allocated for this purpose.
- * @return an array containing the elements of the list.
- * @throws ArrayStoreException if the runtime type of a is not a
- * supertype of the runtime type of every element in this list.
- * @throws NullPointerException if the specified array is null.
+ * @return an array containing the elements of the list
+ * @throws ArrayStoreException if the runtime type of the specified array
+ * is not a supertype of the runtime type of every element in
+ * this list
+ * @throws NullPointerException if the specified array is null
*/
public T[] toArray(T[] a) {
if (a.length < size)
a = (T[])java.lang.reflect.Array.newInstance(
a.getClass().getComponentType(), size);
int i = 0;
- Object[] result = a;
+ Object[] result = a;
for (Entry e = header.next; e != header; e = e.next)
result[i++] = e.element;
@@ -734,17 +929,17 @@ public class LinkedList
*
* @serialData The size of the list (the number of elements it
* contains) is emitted (int), followed by all of its
- * elements (each an Object) in the proper order.
+ * elements (each an Object) in the proper order.
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
- // Write out any hidden serialization magic
- s.defaultWriteObject();
+ // Write out any hidden serialization magic
+ s.defaultWriteObject();
// Write out size
s.writeInt(size);
- // Write out all elements in the proper order.
+ // Write out all elements in the proper order.
for (Entry e = header.next; e != header; e = e.next)
s.writeObject(e.element);
}
@@ -755,8 +950,8 @@ public class LinkedList
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
- // Read in any hidden serialization magic
- s.defaultReadObject();
+ // Read in any hidden serialization magic
+ s.defaultReadObject();
// Read in size
int size = s.readInt();
@@ -765,8 +960,8 @@ public class LinkedList
header = new Entry(null, null, null);
header.next = header.previous = header;
- // Read in all elements in the proper order.
- for (int i=0; i