| 6 |
|
*/ |
| 7 |
|
|
| 8 |
|
package java.util; |
| 9 |
+ |
import java.util.*; // for javadoc (till 6280605 is fixed) |
| 10 |
|
|
| 11 |
|
/** |
| 12 |
|
* Linked list implementation of the <tt>List</tt> interface. Implements all |
| 26 |
|
* list. Operations that index into the list will traverse the list from |
| 27 |
|
* the beginning or the end, whichever is closer to the specified index.<p> |
| 28 |
|
* |
| 29 |
< |
* <b>Note that this implementation is not synchronized.</b> If multiple |
| 30 |
< |
* threads access a list concurrently, and at least one of the threads |
| 31 |
< |
* modifies the list structurally, it <i>must</i> be synchronized |
| 32 |
< |
* externally. (A structural modification is any operation that adds or |
| 33 |
< |
* deletes one or more elements; merely setting the value of an element is not |
| 34 |
< |
* a structural modification.) This is typically accomplished by |
| 35 |
< |
* synchronizing on some object that naturally encapsulates the list. If no |
| 36 |
< |
* such object exists, the list should be "wrapped" using the |
| 37 |
< |
* Collections.synchronizedList method. This is best done at creation time, |
| 38 |
< |
* to prevent accidental unsynchronized access to the list: <pre> |
| 39 |
< |
* List list = Collections.synchronizedList(new LinkedList(...)); |
| 40 |
< |
* </pre> |
| 29 |
> |
* <p><strong>Note that this implementation is not synchronized.</strong> |
| 30 |
> |
* If multiple threads access a linked list concurrently, and at least |
| 31 |
> |
* one of the threads modifies the list structurally, it <i>must</i> be |
| 32 |
> |
* synchronized externally. (A structural modification is any operation |
| 33 |
> |
* that adds or deletes one or more elements; merely setting the value of |
| 34 |
> |
* an element is not a structural modification.) This is typically |
| 35 |
> |
* accomplished by synchronizing on some object that naturally |
| 36 |
> |
* encapsulates the list. |
| 37 |
> |
* |
| 38 |
> |
* If no such object exists, the list should be "wrapped" using the |
| 39 |
> |
* {@link Collections#synchronizedList Collections.synchronizedList} |
| 40 |
> |
* method. This is best done at creation time, to prevent accidental |
| 41 |
> |
* unsynchronized access to the list:<pre> |
| 42 |
> |
* List list = Collections.synchronizedList(new LinkedList(...));</pre> |
| 43 |
|
* |
| 44 |
|
* <p>The iterators returned by this class's <tt>iterator</tt> and |
| 45 |
|
* <tt>listIterator</tt> methods are <i>fail-fast</i>: if the list is |
| 68 |
|
* @see List |
| 69 |
|
* @see ArrayList |
| 70 |
|
* @see Vector |
| 68 |
– |
* @see Collections#synchronizedList(List) |
| 71 |
|
* @since 1.2 |
| 72 |
|
* @param <E> the type of elements held in this collection |
| 73 |
|
*/ |
| 94 |
|
* @param c the collection whose elements are to be placed into this list |
| 95 |
|
* @throws NullPointerException if the specified collection is null |
| 96 |
|
*/ |
| 97 |
< |
public LinkedList(Collection<? extends E> c) { |
| 98 |
< |
this(); |
| 99 |
< |
addAll(c); |
| 100 |
< |
} |
| 97 |
> |
public LinkedList(Collection<? extends E> c) { |
| 98 |
> |
this(); |
| 99 |
> |
addAll(c); |
| 100 |
> |
} |
| 101 |
|
|
| 102 |
|
/** |
| 103 |
|
* Returns the first element in this list. |
| 146 |
|
} |
| 147 |
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|
| 148 |
|
/** |
| 149 |
< |
* Inserts the given element at the beginning of this list. |
| 149 |
> |
* Inserts the specified element at the beginning of this list. |
| 150 |
|
* |
| 151 |
< |
* @param e the element to be inserted at the beginning of this list |
| 151 |
> |
* @param e the element to add |
| 152 |
|
*/ |
| 153 |
|
public void addFirst(E e) { |
| 154 |
|
addBefore(e, header.next); |
| 155 |
|
} |
| 156 |
|
|
| 157 |
|
/** |
| 158 |
< |
* Appends the given element to the end of this list. (Identical in |
| 157 |
< |
* function to the <tt>add</tt> method; included only for consistency.) |
| 158 |
> |
* Appends the specified element to the end of this list. |
| 159 |
|
* |
| 160 |
< |
* @param e the element to be inserted at the end of this list |
| 160 |
> |
* <p>This method is equivalent to {@link #add}. |
| 161 |
> |
* |
| 162 |
> |
* @param e the element to add |
| 163 |
|
*/ |
| 164 |
|
public void addLast(E e) { |
| 165 |
|
addBefore(e, header); |
| 168 |
|
/** |
| 169 |
|
* Returns <tt>true</tt> if this list contains the specified element. |
| 170 |
|
* More formally, returns <tt>true</tt> if and only if this list contains |
| 171 |
< |
* at least one element <tt>e</tt> such that <tt>(o==null ? e==null |
| 172 |
< |
* : o.equals(e))</tt>. |
| 171 |
> |
* at least one element <tt>e</tt> such that |
| 172 |
> |
* <tt>(o==null ? e==null : o.equals(e))</tt>. |
| 173 |
|
* |
| 174 |
|
* @param o element whose presence in this list is to be tested |
| 175 |
|
* @return <tt>true</tt> if this list contains the specified element |
| 190 |
|
/** |
| 191 |
|
* Appends the specified element to the end of this list. |
| 192 |
|
* |
| 193 |
+ |
* <p>This method is equivalent to {@link #addLast}. |
| 194 |
+ |
* |
| 195 |
|
* @param e element to be appended to this list |
| 196 |
< |
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
| 196 |
> |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
| 197 |
|
*/ |
| 198 |
|
public boolean add(E e) { |
| 199 |
|
addBefore(e, header); |
| 201 |
|
} |
| 202 |
|
|
| 203 |
|
/** |
| 204 |
< |
* Removes the first occurrence of the specified element in this list. If |
| 205 |
< |
* the list does not contain the element, it is unchanged. More formally, |
| 206 |
< |
* removes the element with the lowest index <tt>i</tt> such that |
| 207 |
< |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> (if such an |
| 208 |
< |
* element exists). |
| 204 |
> |
* Removes the first occurrence of the specified element from this list, |
| 205 |
> |
* if it is present. If this list does not contain the element, it is |
| 206 |
> |
* unchanged. More formally, removes the element with the lowest index |
| 207 |
> |
* <tt>i</tt> such that |
| 208 |
> |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> |
| 209 |
> |
* (if such an element exists). Returns <tt>true</tt> if this list |
| 210 |
> |
* contained the specified element (or equivalently, if this list |
| 211 |
> |
* changed as a result of the call). |
| 212 |
|
* |
| 213 |
|
* @param o element to be removed from this list, if present |
| 214 |
< |
* @return <tt>true</tt> if the list contained the specified element |
| 214 |
> |
* @return <tt>true</tt> if this list contained the specified element |
| 215 |
|
*/ |
| 216 |
|
public boolean remove(Object o) { |
| 217 |
|
if (o==null) { |
| 237 |
|
* this list, in the order that they are returned by the specified |
| 238 |
|
* collection's iterator. The behavior of this operation is undefined if |
| 239 |
|
* the specified collection is modified while the operation is in |
| 240 |
< |
* progress. (This implies that the behavior of this call is undefined if |
| 241 |
< |
* the specified Collection is this list, and this list is nonempty.) |
| 240 |
> |
* progress. (Note that this will occur if the specified collection is |
| 241 |
> |
* this list, and it's nonempty.) |
| 242 |
|
* |
| 243 |
< |
* @param c the elements to be inserted into this list |
| 243 |
> |
* @param c collection containing elements to be added to this list |
| 244 |
|
* @return <tt>true</tt> if this list changed as a result of the call |
| 245 |
|
* @throws NullPointerException if the specified collection is null |
| 246 |
|
*/ |
| 258 |
|
* |
| 259 |
|
* @param index index at which to insert the first element |
| 260 |
|
* from the specified collection |
| 261 |
< |
* @param c elements to be inserted into this list |
| 261 |
> |
* @param c collection containing elements to be added to this list |
| 262 |
|
* @return <tt>true</tt> if this list changed as a result of the call |
| 263 |
< |
* @throws IndexOutOfBoundsException if the index is out of range |
| 256 |
< |
* (<tt>index < 0 || index > size()</tt>) |
| 263 |
> |
* @throws IndexOutOfBoundsException {@inheritDoc} |
| 264 |
|
* @throws NullPointerException if the specified collection is null |
| 265 |
|
*/ |
| 266 |
|
public boolean addAll(int index, Collection<? extends E> c) { |
| 308 |
|
/** |
| 309 |
|
* Returns the element at the specified position in this list. |
| 310 |
|
* |
| 311 |
< |
* @param index index of element to return |
| 311 |
> |
* @param index index of the element to return |
| 312 |
|
* @return the element at the specified position in this list |
| 313 |
< |
* @throws IndexOutOfBoundsException if the index is out of range |
| 307 |
< |
* (<tt>index < 0 || index > size()</tt>) |
| 313 |
> |
* @throws IndexOutOfBoundsException {@inheritDoc} |
| 314 |
|
*/ |
| 315 |
|
public E get(int index) { |
| 316 |
|
return entry(index).element; |
| 320 |
|
* Replaces the element at the specified position in this list with the |
| 321 |
|
* specified element. |
| 322 |
|
* |
| 323 |
< |
* @param index index of element to replace |
| 323 |
> |
* @param index index of the element to replace |
| 324 |
|
* @param element element to be stored at the specified position |
| 325 |
|
* @return the element previously at the specified position |
| 326 |
< |
* @throws IndexOutOfBoundsException if the index is out of range |
| 321 |
< |
* (<tt>index < 0 || index > size()</tt>) |
| 326 |
> |
* @throws IndexOutOfBoundsException {@inheritDoc} |
| 327 |
|
*/ |
| 328 |
|
public E set(int index, E element) { |
| 329 |
|
Entry<E> e = entry(index); |
| 339 |
|
* |
| 340 |
|
* @param index index at which the specified element is to be inserted |
| 341 |
|
* @param element element to be inserted |
| 342 |
< |
* |
| 338 |
< |
* @throws IndexOutOfBoundsException if the index is out of range |
| 339 |
< |
* (<tt>index < 0 || index > size()</tt>) |
| 342 |
> |
* @throws IndexOutOfBoundsException {@inheritDoc} |
| 343 |
|
*/ |
| 344 |
|
public void add(int index, E element) { |
| 345 |
|
addBefore(element, (index==size ? header : entry(index))); |
| 352 |
|
* |
| 353 |
|
* @param index the index of the element to be removed |
| 354 |
|
* @return the element previously at the specified position |
| 355 |
< |
* |
| 353 |
< |
* @throws IndexOutOfBoundsException if the index is out of range |
| 354 |
< |
* (<tt>index < 0 || index > size()</tt>) |
| 355 |
> |
* @throws IndexOutOfBoundsException {@inheritDoc} |
| 356 |
|
*/ |
| 357 |
|
public E remove(int index) { |
| 358 |
|
return remove(entry(index)); |
| 380 |
|
// Search Operations |
| 381 |
|
|
| 382 |
|
/** |
| 383 |
< |
* Returns the index in this list of the first occurrence of the |
| 384 |
< |
* specified element, or -1 if the List does not contain this |
| 385 |
< |
* element. More formally, returns the lowest index i such that |
| 386 |
< |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if |
| 387 |
< |
* there is no such index. |
| 383 |
> |
* Returns the index of the first occurrence of the specified element |
| 384 |
> |
* in this list, or -1 if this list does not contain the element. |
| 385 |
> |
* More formally, returns the lowest index <tt>i</tt> such that |
| 386 |
> |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, |
| 387 |
> |
* or -1 if there is no such index. |
| 388 |
|
* |
| 389 |
|
* @param o element to search for |
| 390 |
< |
* @return the index in this list of the first occurrence of the |
| 391 |
< |
* specified element, or -1 if the list does not contain this |
| 391 |
< |
* element |
| 390 |
> |
* @return the index of the first occurrence of the specified element in |
| 391 |
> |
* this list, or -1 if this list does not contain the element |
| 392 |
|
*/ |
| 393 |
|
public int indexOf(Object o) { |
| 394 |
|
int index = 0; |
| 409 |
|
} |
| 410 |
|
|
| 411 |
|
/** |
| 412 |
< |
* Returns the index in this list of the last occurrence of the |
| 413 |
< |
* specified element, or -1 if the list does not contain this |
| 414 |
< |
* element. More formally, returns the highest index i such that |
| 415 |
< |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if |
| 416 |
< |
* there is no such index. |
| 412 |
> |
* Returns the index of the last occurrence of the specified element |
| 413 |
> |
* in this list, or -1 if this list does not contain the element. |
| 414 |
> |
* More formally, returns the highest index <tt>i</tt> such that |
| 415 |
> |
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, |
| 416 |
> |
* or -1 if there is no such index. |
| 417 |
|
* |
| 418 |
|
* @param o element to search for |
| 419 |
< |
* @return the index in this list of the last occurrence of the |
| 420 |
< |
* specified element, or -1 if the list does not contain this |
| 421 |
< |
* element |
| 419 |
> |
* @return the index of the last occurrence of the specified element in |
| 420 |
> |
* this list, or -1 if this list does not contain the element |
| 421 |
|
*/ |
| 422 |
|
public int lastIndexOf(Object o) { |
| 423 |
|
int index = size; |
| 486 |
|
* Adds the specified element as the tail (last element) of this list. |
| 487 |
|
* |
| 488 |
|
* @param e the element to add |
| 489 |
< |
* @return <tt>true</tt> (as per the spec for {@link Queue#offer}) |
| 489 |
> |
* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
| 490 |
|
* @since 1.5 |
| 491 |
|
*/ |
| 492 |
|
public boolean offer(E e) { |
| 498 |
|
* Inserts the specified element at the front of this list. |
| 499 |
|
* |
| 500 |
|
* @param e the element to insert |
| 501 |
< |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
| 501 |
> |
* @return <tt>true</tt> (as specified by {@link Deque#offerFirst}) |
| 502 |
|
* @since 1.6 |
| 503 |
|
*/ |
| 504 |
|
public boolean offerFirst(E e) { |
| 510 |
|
* Inserts the specified element at the end of this list. |
| 511 |
|
* |
| 512 |
|
* @param e the element to insert |
| 513 |
< |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
| 513 |
> |
* @return <tt>true</tt> (as specified by {@link Deque#offerLast}) |
| 514 |
|
* @since 1.6 |
| 515 |
|
*/ |
| 516 |
|
public boolean offerLast(E e) { |
| 523 |
|
* or returns <tt>null</tt> if this list is empty. |
| 524 |
|
* |
| 525 |
|
* @return the first element of this list, or <tt>null</tt> |
| 526 |
< |
* if this list is empty. |
| 526 |
> |
* if this list is empty |
| 527 |
|
* @since 1.6 |
| 528 |
|
*/ |
| 529 |
|
public E peekFirst() { |
| 537 |
|
* or returns <tt>null</tt> if this list is empty. |
| 538 |
|
* |
| 539 |
|
* @return the last element of this list, or <tt>null</tt> |
| 540 |
< |
* if this list is empty. |
| 540 |
> |
* if this list is empty |
| 541 |
|
* @since 1.6 |
| 542 |
|
*/ |
| 543 |
|
public E peekLast() { |
| 547 |
|
} |
| 548 |
|
|
| 549 |
|
/** |
| 550 |
< |
* Retrieves and removes the first element of this list, or |
| 551 |
< |
* <tt>null</tt> if this list is empty. |
| 550 |
> |
* Retrieves and removes the first element of this list, |
| 551 |
> |
* or returns <tt>null</tt> if this list is empty. |
| 552 |
|
* |
| 553 |
|
* @return the first element of this list, or <tt>null</tt> if |
| 554 |
|
* this list is empty |
| 561 |
|
} |
| 562 |
|
|
| 563 |
|
/** |
| 564 |
< |
* Retrieves and removes the last element of this list, or |
| 565 |
< |
* <tt>null</tt> if this list is empty. |
| 564 |
> |
* Retrieves and removes the last element of this list, |
| 565 |
> |
* or returns <tt>null</tt> if this list is empty. |
| 566 |
|
* |
| 567 |
|
* @return the last element of this list, or <tt>null</tt> if |
| 568 |
|
* this list is empty |
| 626 |
|
*/ |
| 627 |
|
public boolean removeLastOccurrence(Object o) { |
| 628 |
|
if (o==null) { |
| 629 |
< |
for (Entry e = header.previous; e != header; e = e.previous) { |
| 629 |
> |
for (Entry<E> e = header.previous; e != header; e = e.previous) { |
| 630 |
|
if (e.element==null) { |
| 631 |
|
remove(e); |
| 632 |
|
return true; |
| 633 |
|
} |
| 634 |
|
} |
| 635 |
|
} else { |
| 636 |
< |
for (Entry e = header.previous; e != header; e = e.previous) { |
| 636 |
> |
for (Entry<E> e = header.previous; e != header; e = e.previous) { |
| 637 |
|
if (o.equals(e.element)) { |
| 638 |
|
remove(e); |
| 639 |
|
return true; |
| 658 |
|
* time in the future. |
| 659 |
|
* |
| 660 |
|
* @param index index of the first element to be returned from the |
| 661 |
< |
* list-iterator (by a call to <tt>next</tt>). |
| 661 |
> |
* list-iterator (by a call to <tt>next</tt>) |
| 662 |
|
* @return a ListIterator of the elements in this list (in proper |
| 663 |
< |
* sequence), starting at the specified position in the list. |
| 664 |
< |
* @throws IndexOutOfBoundsException if the index is out of range |
| 666 |
< |
* (<tt>index < 0 || index > size()</tt>). |
| 663 |
> |
* sequence), starting at the specified position in the list |
| 664 |
> |
* @throws IndexOutOfBoundsException {@inheritDoc} |
| 665 |
|
* @see List#listIterator(int) |
| 666 |
|
*/ |
| 667 |
|
public ListIterator<E> listIterator(int index) { |
| 799 |
|
} |
| 800 |
|
|
| 801 |
|
/** |
| 802 |
+ |
* Returns an iterator over the elements in this list in reverse |
| 803 |
+ |
* sequential order. The elements will be returned in order from |
| 804 |
+ |
* last (tail) to first (head). |
| 805 |
+ |
* |
| 806 |
+ |
* @return an iterator over the elements in this list in reverse |
| 807 |
+ |
* sequence |
| 808 |
+ |
*/ |
| 809 |
+ |
public Iterator<E> descendingIterator() { |
| 810 |
+ |
return new DescendingIterator(); |
| 811 |
+ |
} |
| 812 |
+ |
|
| 813 |
+ |
/** Adapter to provide descending iterators via ListItr.previous */ |
| 814 |
+ |
private class DescendingIterator implements Iterator { |
| 815 |
+ |
final ListItr itr = new ListItr(size()); |
| 816 |
+ |
public boolean hasNext() { |
| 817 |
+ |
return itr.hasPrevious(); |
| 818 |
+ |
} |
| 819 |
+ |
public E next() { |
| 820 |
+ |
return itr.previous(); |
| 821 |
+ |
} |
| 822 |
+ |
public void remove() { |
| 823 |
+ |
itr.remove(); |
| 824 |
+ |
} |
| 825 |
+ |
} |
| 826 |
+ |
|
| 827 |
+ |
/** |
| 828 |
|
* Returns a shallow copy of this <tt>LinkedList</tt>. (The elements |
| 829 |
|
* themselves are not cloned.) |
| 830 |
|
* |
| 853 |
|
|
| 854 |
|
/** |
| 855 |
|
* Returns an array containing all of the elements in this list |
| 856 |
< |
* in the correct order. |
| 856 |
> |
* in proper sequence (from first to last element). |
| 857 |
> |
* |
| 858 |
> |
* <p>The returned array will be "safe" in that no references to it are |
| 859 |
> |
* maintained by this list. (In other words, this method must allocate |
| 860 |
> |
* a new array). The caller is thus free to modify the returned array. |
| 861 |
> |
* |
| 862 |
> |
* <p>This method acts as bridge between array-based and collection-based |
| 863 |
> |
* APIs. |
| 864 |
|
* |
| 865 |
|
* @return an array containing all of the elements in this list |
| 866 |
< |
* in the correct order. |
| 866 |
> |
* in proper sequence |
| 867 |
|
*/ |
| 868 |
|
public Object[] toArray() { |
| 869 |
|
Object[] result = new Object[size]; |
| 875 |
|
|
| 876 |
|
/** |
| 877 |
|
* Returns an array containing all of the elements in this list in |
| 878 |
< |
* the correct order; the runtime type of the returned array is that of |
| 879 |
< |
* the specified array. If the list fits in the specified array, it |
| 880 |
< |
* is returned therein. Otherwise, a new array is allocated with the |
| 881 |
< |
* runtime type of the specified array and the size of this list.<p> |
| 882 |
< |
* |
| 883 |
< |
* If the list fits in the specified array with room to spare |
| 884 |
< |
* (i.e., the array has more elements than the list), |
| 885 |
< |
* the element in the array immediately following the end of the |
| 886 |
< |
* collection is set to null. This is useful in determining the length |
| 887 |
< |
* of the list <i>only</i> if the caller knows that the list |
| 888 |
< |
* does not contain any null elements. |
| 878 |
> |
* proper sequence (from first to last element); the runtime type of |
| 879 |
> |
* the returned array is that of the specified array. If the list fits |
| 880 |
> |
* in the specified array, it is returned therein. Otherwise, a new |
| 881 |
> |
* array is allocated with the runtime type of the specified array and |
| 882 |
> |
* the size of this list. |
| 883 |
> |
* |
| 884 |
> |
* <p>If the list fits in the specified array with room to spare (i.e., |
| 885 |
> |
* the array has more elements than the list), the element in the array |
| 886 |
> |
* immediately following the end of the list is set to <tt>null</tt>. |
| 887 |
> |
* (This is useful in determining the length of the list <i>only</i> if |
| 888 |
> |
* the caller knows that the list does not contain any null elements.) |
| 889 |
> |
* |
| 890 |
> |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
| 891 |
> |
* array-based and collection-based APIs. Further, this method allows |
| 892 |
> |
* precise control over the runtime type of the output array, and may, |
| 893 |
> |
* under certain circumstances, be used to save allocation costs. |
| 894 |
> |
* |
| 895 |
> |
* <p>Suppose <tt>x</tt> is a list known to contain only strings. |
| 896 |
> |
* The following code can be used to dump the list into a newly |
| 897 |
> |
* allocated array of <tt>String</tt>: |
| 898 |
> |
* |
| 899 |
> |
* <pre> |
| 900 |
> |
* String[] y = x.toArray(new String[0]);</pre> |
| 901 |
> |
* |
| 902 |
> |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
| 903 |
> |
* <tt>toArray()</tt>. |
| 904 |
|
* |
| 905 |
|
* @param a the array into which the elements of the list are to |
| 906 |
|
* be stored, if it is big enough; otherwise, a new array of the |
| 907 |
|
* same runtime type is allocated for this purpose. |
| 908 |
|
* @return an array containing the elements of the list |
| 909 |
< |
* @throws ArrayStoreException if the runtime type of a is not a |
| 910 |
< |
* supertype of the runtime type of every element in this list |
| 909 |
> |
* @throws ArrayStoreException if the runtime type of the specified array |
| 910 |
> |
* is not a supertype of the runtime type of every element in |
| 911 |
> |
* this list |
| 912 |
|
* @throws NullPointerException if the specified array is null |
| 913 |
|
*/ |
| 914 |
|
public <T> T[] toArray(T[] a) { |
