package systemUnderTest;
import java.util.AbstractSequentialList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
/**
* 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 <tt>LinkedList</tt> 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).
*
* 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.
*
* 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>
*
*
* The iterators returned by the 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.
*
*/
public class LinkedList extends AbstractSequentialList implements List {
private Entry header = new Entry(null, null, null);
private 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.
*/
public LinkedList(Collection c) {
this();
addAll(c);
}
/**
* Returns the first element in this list.
*
* @return the first element in this list.
*/
public Object getFirst() {
if (size == 0)
throw new NoSuchElementException();
// return header.previous.element; //C'EST LOUCHE -->beug
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.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.equals(o)) { // == null --> .element.equals(o)
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.
*
* @throws IndexOutOfBoundsException
* if the specified index is out of range (
* <tt>index < 0 || index > size()</tt>).
*/
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.
* @throws IndexOutOfBoundsException
* if the specified index is out of range (
* <tt>index < 0 || index > size()</tt>).
*/
public boolean addAll(int index, Collection c) {
int numNew = c.size();
if (numNew == 0)
return false;
// modCount++;
// Entry successor = (index == size ? header : entry(index));
// Entry predecessor = successor.previous;
// Iterator it = c.iterator();
// for (int i = 0; i < numNew; i++) {
// Entry e = new Entry(it.next(), successor, predecessor);
// predecessor.next = e;
// predecessor = e;
// }
// successor.previous = predecessor;
int i = index;
for(Object o : c) {
add(i, o);
i++;
}
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 / 2) {
for (int i = 0; i <= index; i++)
e = e.next;
} else {
for (int i = size - 1; i >= index; i--) // ajout/correction: >= au lieu de > simple
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 / 2) {
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() {
LinkedList.this.remove(lastReturned);
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; // ajout
size--;
modCount++;
}
}