--- jsr166/src/main/java/util/LinkedList.java 2003/09/12 15:38:26 1.7
+++ jsr166/src/main/java/util/LinkedList.java 2005/05/16 05:17:07 1.28
@@ -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.
*/
@@ -14,18 +14,16 @@ package java.util;
* the LinkedList class provides uniformly named methods to
* get, remove and insert an element at the
* beginning and end of the list. These operations allow linked lists to be
- * used as a stack, queue, or double-ended queue (deque).
+ * used as a stack, {@linkplain Queue queue}, or {@linkplain Deque
+ * double-ended queue}.
*
- * The class implements the Queue interface, providing
+ * The class implements the Deque interface, providing
* first-in-first-out queue operations for add,
- * poll, etc. Other stack and deque operations could be
- * easily recast in terms of the standard list operations. They're
- * included here primarily for convenience, though they may run
- * slightly faster than the equivalent List operations.
+ * poll, along with other stack and deque operations.
*
* All of the operations perform as could be expected for a doubly-linked
* list. Operations that index into the list will traverse the list from
- * the begining or the end, whichever is closer to the specified index.
+ * 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
@@ -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
@@ -55,9 +54,9 @@ 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.
*
@@ -68,11 +67,12 @@ package java.util;
* @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;
@@ -89,8 +89,8 @@ 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();
@@ -100,8 +100,8 @@ public class LinkedList
/**
* 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 +113,8 @@ 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)
@@ -126,54 +126,50 @@ 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() {
- 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);
}
/**
* 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;
@@ -182,7 +178,7 @@ 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;
@@ -191,24 +187,26 @@ 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).
+ * @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;
}
/**
- * 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) {
@@ -237,9 +235,9 @@ 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);
@@ -253,13 +251,12 @@ public class LinkedList
* in the list in the order that they are returned by the
* specified collection's iterator.
*
- * @param index index at which to insert first element
- * from the specified collection.
- * @param c elements to be inserted into this list.
- * @return true if this list changed as a result of the call.
- * @throws IndexOutOfBoundsException if the specified index is out of
- * range (index < 0 || index > size()).
- * @throws NullPointerException if the specified collection is null.
+ * @param index index at which to insert the first element
+ * from the specified collection
+ * @param c elements to be inserted into 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 c) {
if (index < 0 || index > size)
@@ -288,9 +285,16 @@ 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;
+ size = 0;
+ modCount++;
}
@@ -299,11 +303,9 @@ public class LinkedList
/**
* Returns the element at the specified position in this list.
*
- * @param index index of element to return.
- * @return the element at the specified position in this list.
- *
- * @throws IndexOutOfBoundsException if the specified index is is out of
- * range (index < 0 || index >= size()).
+ * @param index index of the element to return
+ * @return the element at the specified position in this list
+ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E get(int index) {
return entry(index).element;
@@ -313,11 +315,10 @@ public class LinkedList
* Replaces the element at the specified position in this list with the
* specified element.
*
- * @param index index of element to replace.
- * @param element element to be stored at the specified position.
- * @return the element previously at the specified position.
- * @throws IndexOutOfBoundsException if the specified index is out of
- * range (index < 0 || index >= size()).
+ * @param index index of the element to replace
+ * @param element element to be stored at the specified position
+ * @return the element previously at the specified position
+ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E set(int index, E element) {
Entry e = entry(index);
@@ -331,11 +332,9 @@ public class LinkedList
* Shifts the element currently at that position (if any) and any
* subsequent elements to the right (adds one to their indices).
*
- * @param index index at which the specified element is to be inserted.
- * @param element element to be inserted.
- *
- * @throws IndexOutOfBoundsException if the specified index is out of
- * range (index < 0 || index > size()).
+ * @param index index at which the specified element is to be inserted
+ * @param element element to be inserted
+ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
public void add(int index, E element) {
addBefore(element, (index==size ? header : entry(index)));
@@ -346,20 +345,16 @@ public class LinkedList
* subsequent elements to the left (subtracts one from their indices).
* Returns the element that was removed from the list.
*
- * @param index the index of the element to removed.
- * @return the element previously at the specified position.
- *
- * @throws IndexOutOfBoundsException if the specified index is out of
- * range (index < 0 || index >= size()).
+ * @param index the index of the element to be removed
+ * @return the element previously at the specified position
+ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E remove(int index) {
- Entry e = entry(index);
- remove(e);
- return e.element;
+ return remove(entry(index));
}
/**
- * Return the indexed entry.
+ * Returns the indexed entry.
*/
private Entry entry(int index) {
if (index < 0 || index >= size)
@@ -386,10 +381,10 @@ 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.
+ * specified element, or -1 if the list does not contain this
+ * element
*/
public int indexOf(Object o) {
int index = 0;
@@ -416,10 +411,10 @@ 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.
+ * specified element, or -1 if the list does not contain this
+ * element
*/
public int lastIndexOf(Object o) {
int index = size;
@@ -443,7 +438,7 @@ 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() {
@@ -454,8 +449,8 @@ 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() {
@@ -463,8 +458,8 @@ 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() {
@@ -475,8 +470,9 @@ 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() {
@@ -486,13 +482,162 @@ public class LinkedList
/**
* Adds the specified element as the tail (last element) of this list.
*
- * @param x 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 x) {
- return add(x);
+ 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;
}
/**
@@ -509,12 +654,11 @@ 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 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) {
@@ -581,30 +725,31 @@ public class LinkedList
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;
+ next = lastNext;
else
nextIndex--;
lastReturned = header;
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++;
}
@@ -627,8 +772,8 @@ 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++;
@@ -636,21 +781,25 @@ public class LinkedList
return newEntry;
}
- private void remove(Entry e) {
+ 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;
@@ -678,7 +827,7 @@ public class LinkedList
* in the correct order.
*
* @return an array containing all of the elements in this list
- * in the correct order.
+ * in the correct order
*/
public Object[] toArray() {
Object[] result = new Object[size];
@@ -703,12 +852,12 @@ public class LinkedList
* does not contain any null elements.
*
* @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.
+ * 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.
+ * 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)
@@ -732,8 +881,8 @@ 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 {