--- jsr166/src/main/java/util/LinkedList.java 2005/04/26 19:54:03 1.24
+++ jsr166/src/main/java/util/LinkedList.java 2007/05/20 07:54:01 1.47
@@ -1,8 +1,26 @@
/*
- * %W% %E%
+ * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
- * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
+ * 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. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
*/
package java.util;
@@ -25,18 +43,20 @@ package java.util;
* 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.
+ *
+ * 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
@@ -57,7 +77,7 @@ package java.util;
* should be used only to detect bugs.
*
*
This class is a member of the
- *
+ *
* Java Collections Framework.
*
* @author Josh Bloch
@@ -65,7 +85,6 @@ package java.util;
* @see List
* @see ArrayList
* @see Vector
- * @see Collections#synchronizedList(List)
* @since 1.2
* @param the type of elements held in this collection
*/
@@ -89,19 +108,19 @@ 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);
- }
+ public LinkedList(Collection extends E> 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)
@@ -113,8 +132,8 @@ public class LinkedList
/**
* 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)
@@ -126,8 +145,8 @@ public class LinkedList
/**
* 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() {
return remove(header.next);
@@ -136,40 +155,41 @@ public class LinkedList
/**
* 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() {
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.
+ *
+ * This method is equivalent to {@link #add}.
*
- * @param o the element to be inserted at the end of this list.
+ * @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;
@@ -178,7 +198,7 @@ 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;
@@ -187,24 +207,28 @@ public class LinkedList
/**
* 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) {
@@ -230,12 +254,12 @@ 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);
@@ -249,13 +273,12 @@ 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 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)
@@ -302,11 +325,9 @@ 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 index 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;
@@ -316,11 +337,10 @@ 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 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);
@@ -334,11 +354,9 @@ 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 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)));
@@ -349,11 +367,9 @@ 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 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) {
return remove(entry(index));
@@ -381,16 +397,15 @@ 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 +426,15 @@ 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 +458,7 @@ public class LinkedList
/**
* Retrieves, but does not remove, the head (first element) of this list.
- * @return the head of this list, or null if this list is empty.
+ * @return the head of this list, or null if this list is empty
* @since 1.5
*/
public E peek() {
@@ -455,8 +469,8 @@ public class LinkedList
/**
* Retrieves, but does not remove, the head (first element) of this list.
- * @return the head of this list.
- * @throws NoSuchElementException if this list is empty.
+ * @return the head of this list
+ * @throws NoSuchElementException if this list is empty
* @since 1.5
*/
public E element() {
@@ -464,8 +478,8 @@ public class LinkedList
}
/**
- * Retrieves and removes the head (first element) of this list.
- * @return the head of this list, or null if this list 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 +490,9 @@ public class LinkedList
/**
* Retrieves and removes the head (first element) of this list.
- * @return the head of this list.
- * @throws NoSuchElementException if this list is empty.
+ *
+ * @return the head of this list
+ * @throws NoSuchElementException if this list is empty
* @since 1.5
*/
public E remove() {
@@ -487,13 +502,12 @@ 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
@@ -501,7 +515,7 @@ public class LinkedList
* Inserts the specified element at the front of this list.
*
* @param e the element to insert
- * @return true (as per the spec for {@link Deque#offerFirst})
+ * @return true (as specified by {@link Deque#offerFirst})
* @since 1.6
*/
public boolean offerFirst(E e) {
@@ -513,7 +527,7 @@ public class LinkedList
* Inserts the specified element at the end of this list.
*
* @param e the element to insert
- * @return true (as per the spec for {@link Deque#offerLast})
+ * @return true (as specified by {@link Deque#offerLast})
* @since 1.6
*/
public boolean offerLast(E e) {
@@ -523,10 +537,10 @@ public class LinkedList
/**
* Retrieves, but does not remove, the first element of this list,
- * returning null if this list is empty.
+ * or returns null if this list is empty.
*
- * @return the first element of this list, or 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() {
@@ -537,10 +551,10 @@ public class LinkedList
/**
* Retrieves, but does not remove, the last element of this list,
- * returning null if this list is empty.
+ * or returns null if this list is empty.
*
- * @return the last element of this list, or 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() {
@@ -550,8 +564,8 @@ public class LinkedList
}
/**
- * Retrieves and removes the first element of this list, or
- * null if this list is empty.
+ * 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
@@ -564,8 +578,8 @@ public class LinkedList
}
/**
- * Retrieves and removes the last element of this list, or
- * null if this list is empty.
+ * 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
@@ -597,8 +611,8 @@ public class LinkedList
* 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.
+ * of the stack represented by this list)
+ * @throws NoSuchElementException if this list is empty
* @since 1.6
*/
public E pop() {
@@ -629,14 +643,14 @@ public class LinkedList
*/
public boolean removeLastOccurrence(Object o) {
if (o==null) {
- for (Entry e = header.previous; e != header; e = e.previous) {
+ 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) {
+ for (Entry e = header.previous; e != header; e = e.previous) {
if (o.equals(e.element)) {
remove(e);
return true;
@@ -660,12 +674,11 @@ 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 the 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) {
@@ -746,17 +759,17 @@ public class LinkedList
expectedModCount++;
}
- public void set(E o) {
+ public void set(E e) {
if (lastReturned == header)
throw new IllegalStateException();
checkForComodification();
- lastReturned.element = o;
+ lastReturned.element = e;
}
- public void add(E o) {
+ public void add(E e) {
checkForComodification();
lastReturned = header;
- addBefore(o, next);
+ addBefore(e, next);
nextIndex++;
expectedModCount++;
}
@@ -779,8 +792,8 @@ public class LinkedList
}
}
- private Entry addBefore(E o, Entry e) {
- Entry newEntry = new Entry(o, e, e.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++;
@@ -803,10 +816,31 @@ public class LinkedList
}
/**
+ * @since 1.6
+ */
+ public Iterator descendingIterator() {
+ return new DescendingIterator();
+ }
+
+ /** 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;
@@ -831,10 +865,17 @@ 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];
@@ -846,25 +887,41 @@ public class LinkedList
/**
* 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.
+ * 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 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)
@@ -888,8 +945,8 @@ public class LinkedList
* is, serialize it).
*
* @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.
+ * contains) is emitted (int), followed by all of its
+ * elements (each an Object) in the proper order.
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {