| /* |
| * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * 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. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package sun.awt.util; |
| |
| import java.util.AbstractSequentialList; |
| import java.util.Collection; |
| import java.util.ConcurrentModificationException; |
| import java.util.Deque; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.ListIterator; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * Linked list implementation of the <tt>List</tt> interface. Implements all |
| * optional list operations, and permits all elements (including |
| * <tt>null</tt>). In addition to implementing the <tt>List</tt> interface, |
| * the <tt>IdentityLinkedList</tt> class provides uniformly named methods to |
| * <tt>get</tt>, <tt>remove</tt> and <tt>insert</tt> an element at the |
| * beginning and end of the list. These operations allow linked lists to be |
| * used as a stack, {@linkplain Queue queue}, or {@linkplain Deque |
| * double-ended queue}. <p> |
| * |
| * The class implements the <tt>Deque</tt> interface, providing |
| * first-in-first-out queue operations for <tt>add</tt>, |
| * <tt>poll</tt>, along with other stack and deque operations.<p> |
| * |
| * 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.<p> |
| * |
| * <p><strong>Note that this implementation is not synchronized.</strong> |
| * If multiple threads access a linked list concurrently, and at least |
| * one of the threads modifies the list structurally, it <i>must</i> 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:<pre> |
| * List list = Collections.synchronizedList(new IdentityLinkedList(...));</pre> |
| * |
| * <p>The iterators returned by this class's <tt>iterator</tt> and |
| * <tt>listIterator</tt> methods are <i>fail-fast</i>: if the list is |
| * structurally modified at any time after the iterator is created, in |
| * any way except through the Iterator's own <tt>remove</tt> or |
| * <tt>add</tt> 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. |
| * |
| * <p>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 |
| * presence of unsynchronized concurrent modification. Fail-fast iterators |
| * throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
| * Therefore, it would be wrong to write a program that depended on this |
| * exception for its correctness: <i>the fail-fast behavior of iterators |
| * should be used only to detect bugs.</i> |
| */ |
| |
| public class IdentityLinkedList<E> |
| extends AbstractSequentialList<E> |
| implements List<E>, Deque<E> |
| { |
| private transient Entry<E> header = new Entry<E>(null, null, null); |
| private transient int size = 0; |
| |
| /** |
| * Constructs an empty list. |
| */ |
| public IdentityLinkedList() { |
| header.next = header.previous = header; |
| } |
| |
| /** |
| * Constructs a list containing the elements of the specified |
| * 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 |
| */ |
| public IdentityLinkedList(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 |
| */ |
| public E getFirst() { |
| if (size==0) |
| throw new NoSuchElementException(); |
| |
| 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 |
| */ |
| public E getLast() { |
| if (size==0) |
| throw new NoSuchElementException(); |
| |
| 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 |
| */ |
| public E removeFirst() { |
| 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 |
| */ |
| public E removeLast() { |
| return remove(header.previous); |
| } |
| |
| /** |
| * Inserts the specified element at the beginning of this list. |
| * |
| * @param e the element to add |
| */ |
| public void addFirst(E e) { |
| addBefore(e, header.next); |
| } |
| |
| /** |
| * Appends the specified element to the end of this list. |
| * |
| * <p>This method is equivalent to {@link #add}. |
| * |
| * @param e the element to add |
| */ |
| public void addLast(E e) { |
| addBefore(e, header); |
| } |
| |
| /** |
| * Returns <tt>true</tt> if this list contains the specified element. |
| * More formally, returns <tt>true</tt> if and only if this list contains |
| * at least one element <tt>e</tt> such that |
| * <tt>(o==null ? e==null : o == e)</tt>. |
| * |
| * @param o element whose presence in this list is to be tested |
| * @return <tt>true</tt> if this list contains the specified element |
| */ |
| public boolean contains(Object o) { |
| return indexOf(o) != -1; |
| } |
| |
| /** |
| * Returns the number of elements in this list. |
| * |
| * @return the number of elements in this list |
| */ |
| public int size() { |
| return size; |
| } |
| |
| /** |
| * Appends the specified element to the end of this list. |
| * |
| * <p>This method is equivalent to {@link #addLast}. |
| * |
| * @param e element to be appended to this list |
| * @return <tt>true</tt> (as specified by {@link Collection#add}) |
| */ |
| public boolean add(E e) { |
| addBefore(e, header); |
| return true; |
| } |
| |
| /** |
| * 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 |
| * <tt>i</tt> such that <tt>get(i)==o</tt> |
| * (if such an element exists). Returns <tt>true</tt> 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 <tt>true</tt> if this list contained the specified element |
| */ |
| public boolean remove(Object o) { |
| for (Entry<E> e = header.next; e != header; e = e.next) { |
| if (o == e.element) { |
| remove(e); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Appends all of the elements in the specified collection to the end of |
| * 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. (Note that this will occur if the specified collection is |
| * this list, and it's nonempty.) |
| * |
| * @param c collection containing elements to be added to this list |
| * @return <tt>true</tt> 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); |
| } |
| |
| /** |
| * Inserts all of the elements in the specified collection into this |
| * list, starting at the specified position. Shifts the element |
| * currently at that position (if any) and any subsequent elements to |
| * the right (increases their indices). The new elements will appear |
| * in the list in the order that they are returned by the |
| * specified collection's iterator. |
| * |
| * @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 <tt>true</tt> 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) |
| throw new IndexOutOfBoundsException("Index: "+index+ |
| ", Size: "+size); |
| Object[] a = c.toArray(); |
| int numNew = a.length; |
| if (numNew==0) |
| return false; |
| modCount++; |
| |
| Entry<E> successor = (index==size ? header : entry(index)); |
| Entry<E> predecessor = successor.previous; |
| for (int i=0; i<numNew; i++) { |
| Entry<E> e = new Entry<E>((E)a[i], successor, predecessor); |
| predecessor.next = e; |
| predecessor = e; |
| } |
| successor.previous = predecessor; |
| |
| size += numNew; |
| return true; |
| } |
| |
| /** |
| * Removes all of the elements from this list. |
| */ |
| public void clear() { |
| Entry<E> e = header.next; |
| while (e != header) { |
| Entry<E> next = e.next; |
| e.next = e.previous = null; |
| e.element = null; |
| e = next; |
| } |
| header.next = header.previous = header; |
| size = 0; |
| modCount++; |
| } |
| |
| |
| // Positional Access Operations |
| |
| /** |
| * Returns the element at the specified position in this list. |
| * |
| * @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; |
| } |
| |
| /** |
| * Replaces the element at the specified position in this list with the |
| * specified element. |
| * |
| * @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> e = entry(index); |
| E oldVal = e.element; |
| e.element = element; |
| return oldVal; |
| } |
| |
| /** |
| * Inserts the specified element at the specified position in this list. |
| * 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 {@inheritDoc} |
| */ |
| public void add(int index, E element) { |
| addBefore(element, (index==size ? header : entry(index))); |
| } |
| |
| /** |
| * Removes the element at the specified position in this list. Shifts any |
| * 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 be removed |
| * @return the element previously at the specified position |
| * @throws IndexOutOfBoundsException {@inheritDoc} |
| */ |
| public E remove(int index) { |
| return remove(entry(index)); |
| } |
| |
| /** |
| * Returns the indexed entry. |
| */ |
| private Entry<E> entry(int index) { |
| if (index < 0 || index >= size) |
| throw new IndexOutOfBoundsException("Index: "+index+ |
| ", Size: "+size); |
| Entry<E> e = header; |
| if (index < (size >> 1)) { |
| for (int i = 0; i <= index; i++) |
| e = e.next; |
| } else { |
| for (int i = size; i > index; i--) |
| e = e.previous; |
| } |
| return e; |
| } |
| |
| |
| // Search Operations |
| |
| /** |
| * 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 <tt>i</tt> such that |
| * <tt>get(i)==o</tt>, |
| * 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; |
| for (Entry e = header.next; e != header; e = e.next) { |
| if (o == e.element) { |
| return index; |
| } |
| index++; |
| } |
| return -1; |
| } |
| |
| /** |
| * 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 <tt>i</tt> such that |
| * <tt>get(i)==o</tt>, |
| * 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; |
| for (Entry e = header.previous; e != header; e = e.previous) { |
| index--; |
| if (o == e.element) { |
| return index; |
| } |
| } |
| return -1; |
| } |
| |
| // Queue operations. |
| |
| /** |
| * Retrieves, but does not remove, the head (first element) of this list. |
| * @return the head of this list, or <tt>null</tt> if this list is empty |
| * @since 1.5 |
| */ |
| public E peek() { |
| if (size==0) |
| return null; |
| return getFirst(); |
| } |
| |
| /** |
| * 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 |
| * @since 1.5 |
| */ |
| public E element() { |
| return getFirst(); |
| } |
| |
| /** |
| * Retrieves and removes the head (first element) of this list |
| * @return the head of this list, or <tt>null</tt> if this list is empty |
| * @since 1.5 |
| */ |
| public E poll() { |
| if (size==0) |
| return null; |
| return removeFirst(); |
| } |
| |
| /** |
| * Retrieves and removes the head (first element) of this list. |
| * |
| * @return the head of this list |
| * @throws NoSuchElementException if this list is empty |
| * @since 1.5 |
| */ |
| public E remove() { |
| return removeFirst(); |
| } |
| |
| /** |
| * Adds the specified element as the tail (last element) of this list. |
| * |
| * @param e the element to add |
| * @return <tt>true</tt> (as specified by {@link Queue#offer}) |
| * @since 1.5 |
| */ |
| 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 <tt>true</tt> (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 <tt>true</tt> (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 <tt>null</tt> if this list is empty. |
| * |
| * @return the first element of this list, or <tt>null</tt> |
| * 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 <tt>null</tt> if this list is empty. |
| * |
| * @return the last element of this list, or <tt>null</tt> |
| * 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 <tt>null</tt> if this list is empty. |
| * |
| * @return the first element of this list, or <tt>null</tt> 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 <tt>null</tt> if this list is empty. |
| * |
| * @return the last element of this list, or <tt>null</tt> 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. |
| * |
| * <p>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. |
| * |
| * <p>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 <tt>true</tt> 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 <tt>true</tt> if the list contained the specified element |
| * @since 1.6 |
| */ |
| public boolean removeLastOccurrence(Object o) { |
| for (Entry<E> e = header.previous; e != header; e = e.previous) { |
| if (o == e.element) { |
| remove(e); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Returns a list-iterator of the elements in this list (in proper |
| * sequence), starting at the specified position in the list. |
| * Obeys the general contract of <tt>List.listIterator(int)</tt>.<p> |
| * |
| * The list-iterator is <i>fail-fast</i>: if the list is structurally |
| * modified at any time after the Iterator is created, in any way except |
| * through the list-iterator's own <tt>remove</tt> or <tt>add</tt> |
| * methods, the list-iterator will throw a |
| * <tt>ConcurrentModificationException</tt>. 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. |
| * |
| * @param index index of the first element to be returned from the |
| * list-iterator (by a call to <tt>next</tt>) |
| * @return a ListIterator of the elements in this list (in proper |
| * sequence), starting at the specified position in the list |
| * @throws IndexOutOfBoundsException {@inheritDoc} |
| * @see List#listIterator(int) |
| */ |
| public ListIterator<E> listIterator(int index) { |
| return new ListItr(index); |
| } |
| |
| private class ListItr implements ListIterator<E> { |
| private Entry<E> lastReturned = header; |
| private Entry<E> 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; nextIndex<index; nextIndex++) |
| next = next.next; |
| } else { |
| next = header; |
| for (nextIndex=size; nextIndex>index; 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 void remove() { |
| checkForComodification(); |
| Entry<E> lastNext = lastReturned.next; |
| try { |
| IdentityLinkedList.this.remove(lastReturned); |
| } catch (NoSuchElementException e) { |
| throw new IllegalStateException(); |
| } |
| if (next==lastReturned) |
| next = lastNext; |
| else |
| 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> { |
| E element; |
| Entry<E> next; |
| Entry<E> previous; |
| |
| Entry(E element, Entry<E> next, Entry<E> previous) { |
| this.element = element; |
| this.next = next; |
| this.previous = previous; |
| } |
| } |
| |
| private Entry<E> addBefore(E e, Entry<E> entry) { |
| Entry<E> newEntry = new Entry<E>(e, entry, entry.previous); |
| newEntry.previous.next = newEntry; |
| newEntry.next.previous = newEntry; |
| size++; |
| modCount++; |
| return newEntry; |
| } |
| |
| private E remove(Entry<E> 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<E> 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 an array containing all of the elements in this list |
| * in proper sequence (from first to last element). |
| * |
| * <p>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. |
| * |
| * <p>This method acts as bridge between array-based and collection-based |
| * APIs. |
| * |
| * @return an array containing all of the elements in this list |
| * in proper sequence |
| */ |
| public Object[] toArray() { |
| Object[] result = new Object[size]; |
| int i = 0; |
| for (Entry<E> e = header.next; e != header; e = e.next) |
| result[i++] = e.element; |
| return result; |
| } |
| |
| /** |
| * Returns an array containing all of the elements in this list in |
| * 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. |
| * |
| * <p>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 <tt>null</tt>. |
| * (This is useful in determining the length of the list <i>only</i> if |
| * the caller knows that the list does not contain any null elements.) |
| * |
| * <p>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. |
| * |
| * <p>Suppose <tt>x</tt> is a list known to contain only strings. |
| * The following code can be used to dump the list into a newly |
| * allocated array of <tt>String</tt>: |
| * |
| * <pre> |
| * String[] y = x.toArray(new String[0]);</pre> |
| * |
| * Note that <tt>toArray(new Object[0])</tt> is identical in function to |
| * <tt>toArray()</tt>. |
| * |
| * @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 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> 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; |
| for (Entry<E> e = header.next; e != header; e = e.next) |
| result[i++] = e.element; |
| |
| if (a.length > size) |
| a[size] = null; |
| |
| return a; |
| } |
| } |
