--- jsr166/src/main/java/util/LinkedList.java 2003/05/14 21:30:44 1.1
+++ jsr166/src/main/java/util/LinkedList.java 2005/05/16 05:17:07 1.28
@@ -1,30 +1,29 @@
/*
- * @(#)LinkedList.java 1.43 01/12/03
+ * %W% %E%
*
- * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
+ * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
/**
- * JSR166: Added Queue operations.
* Linked list implementation of the List interface. Implements all
* optional list operations, and permits all elements (including
* null). In addition to implementing the List interface,
* 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}.
*
- * All of the stack/queue/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.
+ * The class implements the Deque interface, providing
+ * first-in-first-out queue operations for add,
+ * 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
@@ -37,38 +36,45 @@ 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
* presence of unsynchronized concurrent modification. Fail-fast iterators
- * throw ConcurrentModificationException on a best-effort basis.
+ * 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.
*
+ *
This class is a member of the
+ *
+ * Java Collections Framework.
+ *
* @author Josh Bloch
- * @version 1.43, 12/03/01
- * @see java.util.List
- * @see java.util.ArrayList
- * @see java.util.Vector
- * @see java.util.Collections#synchronizedList(java.util.List)
+ * @version %I%, %G%
+ * @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
+public class LinkedList
+ extends AbstractSequentialList
+ implements List, Deque, Cloneable, java.io.Serializable
{
- private transient Entry header = new Entry(null, null, null);
+ private transient Entry header = new Entry(null, null, null);
private transient int size = 0;
/**
@@ -83,91 +89,87 @@ public class LinkedList extends Abstract
* 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 Object getFirst() {
- if (size==0)
- throw new NoSuchElementException();
+ public E getFirst() {
+ 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 Object getLast() {
- if (size==0)
- throw new NoSuchElementException();
+ public E getLast() {
+ 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 Object removeFirst() {
- Object first = header.next.element;
- remove(header.next);
- return first;
+ 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.
+ * @return the last element from this list
+ * @throws NoSuchElementException if this list is empty
*/
- public Object removeLast() {
- Object last = header.previous.element;
- remove(header.previous);
- return last;
+ public E removeLast() {
+ 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(Object 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(Object 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;
@@ -176,44 +178,46 @@ public class LinkedList extends Abstract
/**
* 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(Object 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) {
- for (Entry e = header.next; e != header; e = e.next) {
+ for (Entry e = header.next; e != header; e = e.next) {
if (e.element==null) {
remove(e);
return true;
}
}
} else {
- for (Entry e = header.next; e != header; e = e.next) {
+ for (Entry e = header.next; e != header; e = e.next) {
if (o.equals(e.element)) {
remove(e);
return true;
@@ -231,11 +235,11 @@ public class LinkedList extends Abstract
* 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) {
+ public boolean addAll(Collection c) {
return addAll(size, c);
}
@@ -247,25 +251,27 @@ public class LinkedList extends Abstract
* 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) {
- int numNew = c.size();
+ public boolean addAll(int index, Collection 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++;
+ modCount++;
- Entry successor = (index==size ? header : entry(index));
- Entry predecessor = successor.previous;
- Iterator it = c.iterator();
- for (int i=0; i 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;
}
@@ -279,9 +285,16 @@ public class LinkedList extends Abstract
* 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++;
}
@@ -290,13 +303,11 @@ public class LinkedList extends Abstract
/**
* 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 Object get(int index) {
+ public E get(int index) {
return entry(index).element;
}
@@ -304,15 +315,14 @@ public class LinkedList extends Abstract
* 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()).
- */
- public Object set(int index, Object element) {
- Entry e = entry(index);
- Object oldVal = e.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 = entry(index);
+ E oldVal = e.element;
e.element = element;
return oldVal;
}
@@ -322,13 +332,11 @@ public class LinkedList extends Abstract
* 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, Object element) {
+ public void add(int index, E element) {
addBefore(element, (index==size ? header : entry(index)));
}
@@ -337,26 +345,22 @@ public class LinkedList extends Abstract
* 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 Object remove(int index) {
- Entry e = entry(index);
- remove(e);
- return e.element;
+ public E remove(int index) {
+ return remove(entry(index));
}
/**
- * Return the indexed entry.
+ * Returns the indexed entry.
*/
- private Entry entry(int index) {
+ private Entry entry(int index) {
if (index < 0 || index >= size)
throw new IndexOutOfBoundsException("Index: "+index+
", Size: "+size);
- Entry e = header;
+ Entry e = header;
if (index < (size >> 1)) {
for (int i = 0; i <= index; i++)
e = e.next;
@@ -377,10 +381,10 @@ public class LinkedList extends Abstract
* (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;
@@ -407,10 +411,10 @@ public class LinkedList extends Abstract
* (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;
@@ -430,6 +434,212 @@ public class LinkedList extends Abstract
return -1;
}
+ // Queue operations.
+
+ /**
+ * Retrieves, but does not remove, the head (first element) of this list.
+ * @return the head of this list, or null if this list is empty
+ * @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 null 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 true (as per the spec for {@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 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;
+ }
+
/**
* Returns a list-iterator of the elements in this list (in proper
* sequence), starting at the specified position in the list.
@@ -444,165 +654,169 @@ public class LinkedList extends Abstract
* 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()).
- * @see java.util.List#listIterator(int)
- */
- public ListIterator listIterator(int 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;
- }
-
- public Object next() {
- checkForComodification();
- if (nextIndex == size)
- throw new NoSuchElementException();
-
- lastReturned = next;
- next = next.next;
- nextIndex++;
- return lastReturned.element;
- }
-
- public boolean hasPrevious() {
- return nextIndex != 0;
- }
-
- public Object previous() {
- if (nextIndex == 0)
- throw new NoSuchElementException();
-
- lastReturned = next = next.previous;
- nextIndex--;
- checkForComodification();
- return lastReturned.element;
- }
+ * sequence), starting at the specified position in the list
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @see List#listIterator(int)
+ */
+ public ListIterator listIterator(int 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;
+ }
+
+ 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 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(Object o) {
- if (lastReturned == header)
- throw new IllegalStateException();
- checkForComodification();
- lastReturned.element = o;
- }
-
- public void add(Object o) {
- checkForComodification();
- lastReturned = header;
- addBefore(o, next);
- nextIndex++;
- expectedModCount++;
- }
-
- final void checkForComodification() {
- if (modCount != expectedModCount)
- throw new ConcurrentModificationException();
- }
- }
-
- private static class Entry {
- Object element;
- Entry next;
- Entry previous;
-
- Entry(Object element, Entry next, Entry previous) {
- this.element = element;
- this.next = next;
- this.previous = previous;
- }
- }
-
- private Entry addBefore(Object 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++;
+ 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 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();
- }
+ LinkedList clone = null;
+ try {
+ clone = (LinkedList) super.clone();
+ } catch (CloneNotSupportedException e) {
+ throw new InternalError();
+ }
// Put clone into "virgin" state
- clone.header = new Entry(null, null, null);
+ clone.header = new Entry(null, null, null);
clone.header.next = clone.header.previous = clone.header;
clone.size = 0;
clone.modCount = 0;
// Initialize clone with our elements
- for (Entry e = header.next; e != header; e = e.next)
+ for (Entry e = header.next; e != header; e = e.next)
clone.add(e.element);
return clone;
@@ -613,14 +827,14 @@ public class LinkedList extends Abstract
* 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];
+ Object[] result = new Object[size];
int i = 0;
- for (Entry e = header.next; e != header; e = e.next)
+ for (Entry e = header.next; e != header; e = e.next)
result[i++] = e.element;
- return result;
+ return result;
}
/**
@@ -640,18 +854,19 @@ public class LinkedList extends Abstract
* @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 Object[] toArray(Object a[]) {
+ public T[] toArray(T[] a) {
if (a.length < size)
- a = (Object[])java.lang.reflect.Array.newInstance(
+ a = (T[])java.lang.reflect.Array.newInstance(
a.getClass().getComponentType(), size);
int i = 0;
- for (Entry e = header.next; e != header; e = e.next)
- a[i++] = e.element;
+ Object[] result = a;
+ for (Entry e = header.next; e != header; e = e.next)
+ result[i++] = e.element;
if (a.length > size)
a[size] = null;
@@ -667,17 +882,17 @@ public class LinkedList extends Abstract
*
* @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 synchronized void writeObject(java.io.ObjectOutputStream s)
+ 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);
}
@@ -686,53 +901,20 @@ public class LinkedList extends Abstract
* Reconstitute this LinkedList instance from a stream (that is
* deserialize it).
*/
- private synchronized void readObject(java.io.ObjectInputStream s)
+ 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();
// Initialize header
- header = new Entry(null, null, null);
+ header = new Entry(null, null, null);
header.next = header.previous = header;
- // Read in all elements in the proper order.
- for (int i=0; i