Værsgo... jeg snippede lige koden fra src.zip i min java installation....
/*
* @(#)LinkedList.java 1.46 03/01/23
*
* Copyright 2003 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
/**
* 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>LinkedList</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, queue, or double-ended queue (deque).<p>
*
* 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.<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 begining or the end, whichever is closer to the specified index.<p>
*
* <b>Note that this implementation is not synchronized.</b> If multiple
* threads access a 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
* Collections.synchronizedList method. This is best done at creation time,
* to prevent accidental unsynchronized access to the list: <pre>
* List list = Collections.synchronizedList(new LinkedList(...));
* </pre><p>
*
* The iterators returned by the 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 <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.
*
* <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><p>
*
* This class is a member of the
* <a href="{@docRoot}/../guide/collections/index.html">
* Java Collections Framework</a>.
*
* @author Josh Bloch
* @version 1.46, 01/23/03
* @see List
* @see ArrayList
* @see Vector
* @see Collections#synchronizedList(List)
* @since 1.2
*/
public class LinkedList extends AbstractSequentialList
implements List, Cloneable, java.io.Serializable
{
private transient Entry header = new Entry(null, null, null);
private transient int size = 0;
/**
* Constructs an empty list.
*/
public LinkedList() {
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 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.
*/
public Object 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 Object 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 Object removeFirst() {
Object first = header.next.element;
remove(header.next);
return first;
}
/**
* Removes and returns the last element from this list.
*
* @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;
}
/**
* Inserts the given element at the beginning of this list.
*
* @param o the element to be inserted at the beginning of this list.
*/
public void addFirst(Object o) {
addBefore(o, header.next);
}
/**
* Appends the given element to the end of this list. (Identical in
* function to the <tt>add</tt> method; included only for consistency.)
*
* @param o the element to be inserted at the end of this list.
*/
public void addLast(Object o) {
addBefore(o, 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.equals(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.
*
* @param o element to be appended to this list.
* @return <tt>true</tt> (as per the general contract of
* <tt>Collection.add</tt>).
*/
public boolean add(Object o) {
addBefore(o, 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 <tt>i</tt> such that
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> (if such an
* element exists).
*
* @param o element to be removed from this list, if present.
* @return <tt>true</tt> if the list contained the specified element.
*/
public boolean remove(Object o) {
if (o==null) {
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) {
if (o.equals(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. (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 <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 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 first element
* from the specified collection.
* @param c elements to be inserted into this list.
* @return <tt>true</tt> if this list changed as a result of the call.
* @throws IndexOutOfBoundsException if the specified index is out of
* range (<tt>index < 0 || index > size()</tt>).
* @throws NullPointerException if the specified collection is null.
*/
public boolean addAll(int index, Collection c) {
Object[] a = c.toArray();
int numNew = a.length;
if (numNew==0)
return false;
modCount++;
Entry successor = (index==size ? header : entry(index));
Entry predecessor = successor.previous;
for (int i=0; i<numNew; i++) {
Entry e = new Entry(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() {
modCount++;
header.next = header.previous = header;
size = 0;
}
// Positional Access Operations
/**
* 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 (<tt>index < 0 || index >= size()</tt>).
*/
public Object 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 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 (<tt>index < 0 || index >= size()</tt>).
*/
public Object set(int index, Object element) {
Entry e = entry(index);
Object 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 if the specified index is out of
* range (<tt>index < 0 || index > size()</tt>).
*/
public void add(int index, Object 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 removed.
* @return the element previously at the specified position.
*
* @throws IndexOutOfBoundsException if the specified index is out of
* range (<tt>index < 0 || index >= size()</tt>).
*/
public Object remove(int index) {
Entry e = entry(index);
remove(e);
return e.element;
}
/**
* Return the indexed entry.
*/
private Entry entry(int index) {
if (index < 0 || index >= size)
throw new IndexOutOfBoundsException("Index: "+index+
", Size: "+size);
Entry 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 in this list of the first occurrence of the
* specified element, or -1 if the List does not contain this
* element. More formally, returns the lowest index i such that
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if
* there is no such index.
*
* @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.
*/
public int indexOf(Object o) {
int index = 0;
if (o==null) {
for (Entry e = header.next; e != header; e = e.next) {
if (e.element==null)
return index;
index++;
}
} else {
for (Entry e = header.next; e != header; e = e.next) {
if (o.equals(e.element))
return index;
index++;
}
}
return -1;
}
/**
* Returns the index in this list of the last occurrence of the
* specified element, or -1 if the list does not contain this
* element. More formally, returns the highest index i such that
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if
* there is no such index.
*
* @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.
*/
public int lastIndexOf(Object o) {
int index = size;
if (o==null) {
for (Entry e = header.previous; e != header; e = e.previous) {
index--;
if (e.element==null)
return index;
}
} else {
for (Entry e = header.previous; e != header; e = e.previous) {
index--;
if (o.equals(e.element))
return index;
}
}
return -1;
}
/**
* 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 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 if index is out of range
* (<tt>index < 0 || index > size()</tt>).
* @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; 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 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;
}
public int nextIndex() {
return nextIndex;
}
public int previousIndex() {
return nextIndex-1;
}
public void remove() {
checkForComodification();
try {
LinkedList.this.remove(lastReturned);
} catch (NoSuchElementException e) {
throw new IllegalStateException();
}
if (next==lastReturned)
next = lastReturned.next;
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++;
}
/**
* Returns a shallow copy of this <tt>LinkedList</tt>. (The elements
* themselves are not cloned.)
*
* @return a shallow copy of this <tt>LinkedList</tt> instance.
*/
public Object clone() {
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.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)
clone.add(e.element);
return clone;
}
/**
* Returns an array containing all of the elements in this list
* in the correct order.
*
* @return an array containing all of the elements in this list
* in the correct order.
*/
public Object[] toArray() {
Object[] result = new Object[size];
int i = 0;
for (Entry 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
* the correct order; 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
* collection is set to null. 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.
*
* @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 a is not a
* supertype of the runtime type of every element in this list.
* @throws NullPointerException if the specified array is null.
*/
public Object[] toArray(Object a[]) {
if (a.length < size)
a = (Object[])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;
if (a.length > size)
a[size] = null;
return a;
}
private static final long serialVersionUID = 876323262645176354L;
/**
* Save the state of this <tt>LinkedList</tt> instance to a stream (that
* 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.
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
// Write out any hidden serialization magic
s.defaultWriteObject();
// Write out size
s.writeInt(size);
// Write out all elements in the proper order.
for (Entry e = header.next; e != header; e = e.next)
s.writeObject(e.element);
}
/**
* Reconstitute this <tt>LinkedList</tt> instance from a stream (that is
* deserialize it).
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in any hidden serialization magic
s.defaultReadObject();
// Read in size
int size = s.readInt();
// Initialize header
header = new Entry(null, null, null);
header.next = header.previous = header;
// Read in all elements in the proper order.
for (int i=0; i<size; i++)
add(s.readObject());
}
}
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