--- jsr166/src/main/java/util/LinkedList.java 2003/11/17 08:09:34 1.13 +++ jsr166/src/main/java/util/LinkedList.java 2005/05/14 02:19:00 1.27 @@ -1,7 +1,7 @@ /* * %W% %E% * - * Copyright 2003 Sun Microsystems, Inc. All rights reserved. + * Copyright 2005 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ @@ -14,14 +14,12 @@ 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 @@ -38,16 +36,17 @@ package java.util; * 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 the this class's iterator and + *

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 +54,25 @@ 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 + * @see Collections#synchronizedList(List) * @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; @@ -90,81 +89,77 @@ 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 c) { - this(); - addAll(c); - } + public LinkedList(Collection 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. * - * @param o the element to be inserted at the beginning of this list. + * @param e the element to be inserted at the beginning of this list */ - 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.) * - * @param o the element to be inserted at the end of this list. + * @param e the element to be inserted at the end of this list */ - public void addLast(E o) { - addBefore(o, header); + public void addLast(E e) { + addBefore(e, header); } /** @@ -173,8 +168,8 @@ public class LinkedList * 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; @@ -183,21 +178,20 @@ 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). + * @param e element to be appended to this list + * @return true (as per the spec for {@link Collection#add}) */ - public boolean add(E o) { - addBefore(o, header); + public boolean add(E e) { + addBefore(e, header); return true; } @@ -208,8 +202,8 @@ public class LinkedList * (o==null ? get(i)==null : o.equals(get(i))) (if such an * element exists). * - * @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 the list contained the specified element */ public boolean remove(Object o) { if (o==null) { @@ -238,9 +232,9 @@ public class LinkedList * progress. (This implies that the behavior of this call is undefined if * the specified Collection is this list, and this list is 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 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 */ public boolean addAll(Collection c) { return addAll(size, c); @@ -254,13 +248,13 @@ 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 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 */ public boolean addAll(int index, Collection c) { if (index < 0 || index > size) @@ -270,11 +264,11 @@ 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 +283,16 @@ 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 +301,10 @@ 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 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()) */ public E get(int index) { return entry(index).element; @@ -314,11 +314,11 @@ 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 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()) */ public E set(int index, E element) { Entry e = entry(index); @@ -332,11 +332,11 @@ 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. + * @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()). + * @throws IndexOutOfBoundsException if the index is out of range + * (index < 0 || index > size()) */ public void add(int index, E element) { addBefore(element, (index==size ? header : entry(index))); @@ -347,20 +347,18 @@ 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. + * @param index the index of the element to be removed + * @return the element previously at the specified position * - * @throws IndexOutOfBoundsException if the specified index is out of - * range (index < 0 || index >= size()). + * @throws IndexOutOfBoundsException if the index is out of range + * (index < 0 || index > size()) */ 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) @@ -387,10 +385,10 @@ public class LinkedList * (o==null ? get(i)==null : o.equals(get(i))), or -1 if * there is no such index. * - * @param o element to search for. + * @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. + * element */ public int indexOf(Object o) { int index = 0; @@ -417,10 +415,10 @@ public class LinkedList * (o==null ? get(i)==null : o.equals(get(i))), or -1 if * there is no such index. * - * @param o element to search for. + * @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. + * element */ public int lastIndexOf(Object o) { int index = size; @@ -444,7 +442,7 @@ 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 +453,8 @@ 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 +462,8 @@ 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 +474,9 @@ 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 +486,162 @@ 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 per the spec for {@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 per the spec for {@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 per the spec for {@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 + * 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 + * 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 +658,161 @@ 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 + * @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()). + * @throws IndexOutOfBoundsException if the index is out of range + * (index < 0 || index > size()). * @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; - } - } - - 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++; + 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; } /** * 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); @@ -682,11 +835,11 @@ public class LinkedList * in the correct order. */ 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; } /** @@ -706,17 +859,17 @@ public class LinkedList * @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. + * @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. + * 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 +887,17 @@ 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 +908,8 @@ 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 +918,8 @@ 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