/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.sglj.util;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.Array;
import java.util.AbstractSequentialList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Deque;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
/**
* LinkedList is an implementation of List, backed by a linked list. All
* optional operations (adding, removing and replacing) are supported. The
* elements can be any objects.<br>
*
* Unlike the {@link java.util.LinkedList}, this implementation
* has the {@link #concatenate(LinkedList)} method which merges
* two linked lists in constant time.
*
*/
public class LinkedList<E> extends AbstractSequentialList<E> implements
List<E>, Deque<E>, Cloneable, Serializable {
private static final long serialVersionUID = 876323262645176354L;
transient int size = 0;
transient Link<E> voidLink;
private static final class Link<ET> {
ET data;
Link<ET> previous, next;
Link(ET o, Link<ET> p, Link<ET> n) {
data = o;
previous = p;
next = n;
}
}
private static final class LinkIterator<ET> implements ListIterator<ET> {
int pos, expectedModCount;
final LinkedList<ET> list;
Link<ET> link, lastLink;
LinkIterator(LinkedList<ET> object, int location) {
list = object;
expectedModCount = list.modCount;
if (0 <= location && location <= list.size) {
// pos ends up as -1 if list is empty, it ranges from -1 to
// list.size - 1
// if link == voidLink then pos must == -1
link = list.voidLink;
if (location < list.size / 2) {
for (pos = -1; pos + 1 < location; pos++) {
link = link.next;
}
} else {
for (pos = list.size; pos >= location; pos--) {
link = link.previous;
}
}
} else {
throw new IndexOutOfBoundsException();
}
}
public void add(ET object) {
if (expectedModCount == list.modCount) {
Link<ET> next = link.next;
Link<ET> newLink = new Link<ET>(object, link, next);
link.next = newLink;
next.previous = newLink;
link = newLink;
lastLink = null;
pos++;
expectedModCount++;
list.size++;
list.modCount++;
} else {
throw new ConcurrentModificationException();
}
}
public boolean hasNext() {
return link.next != list.voidLink;
}
public boolean hasPrevious() {
return link != list.voidLink;
}
public ET next() {
if (expectedModCount == list.modCount) {
LinkedList.Link<ET> next = link.next;
if (next != list.voidLink) {
lastLink = link = next;
pos++;
return link.data;
}
throw new NoSuchElementException();
}
throw new ConcurrentModificationException();
}
public int nextIndex() {
return pos + 1;
}
public ET previous() {
if (expectedModCount == list.modCount) {
if (link != list.voidLink) {
lastLink = link;
link = link.previous;
pos--;
return lastLink.data;
}
throw new NoSuchElementException();
}
throw new ConcurrentModificationException();
}
public int previousIndex() {
return pos;
}
public void remove() {
if (expectedModCount == list.modCount) {
if (lastLink != null) {
Link<ET> next = lastLink.next;
Link<ET> previous = lastLink.previous;
next.previous = previous;
previous.next = next;
if (lastLink == link) {
pos--;
}
link = previous;
lastLink = null;
expectedModCount++;
list.size--;
list.modCount++;
} else {
throw new IllegalStateException();
}
} else {
throw new ConcurrentModificationException();
}
}
public void set(ET object) {
if (expectedModCount == list.modCount) {
if (lastLink != null) {
lastLink.data = object;
} else {
throw new IllegalStateException();
}
} else {
throw new ConcurrentModificationException();
}
}
}
private static final class DescendingIterator<E> implements Iterator<E> {
final LinkIterator<E> itr;
public DescendingIterator(LinkedList<E> object) {
this.itr = new LinkIterator<E>(object, object.size());
}
public boolean hasNext() {
return itr.hasPrevious();
}
public E next() {
return itr.previous();
}
public void remove() {
itr.remove();
}
}
/**
* Constructs a new empty instance of {@code LinkedList}.
*/
public LinkedList() {
voidLink = new Link<E>(null, null, null);
voidLink.previous = voidLink;
voidLink.next = voidLink;
}
/**
* Constructs a new instance of {@code LinkedList} that holds all of the
* elements contained in the specified {@code collection}. The order of the
* elements in this new {@code LinkedList} will be determined by the
* iteration order of {@code collection}.
*
* @param collection
* the collection of elements to add.
*/
public LinkedList(Collection<? extends E> collection) {
this();
addAll(collection);
}
/**
* Inserts the specified object into this {@code LinkedList} at the
* specified location. The object is inserted before any previous element at
* the specified location. If the location is equal to the size of this
* {@code LinkedList}, the object is added at the end.
*
* @param location
* the index at which to insert.
* @param object
* the object to add.
* @throws IndexOutOfBoundsException
* if {@code location < 0 || >= size()}
*/
@Override
public void add(int location, E object) {
if (0 <= location && location <= size) {
Link<E> link = voidLink;
if (location < (size / 2)) {
for (int i = 0; i <= location; i++) {
link = link.next;
}
} else {
for (int i = size; i > location; i--) {
link = link.previous;
}
}
Link<E> previous = link.previous;
Link<E> newLink = new Link<E>(object, previous, link);
previous.next = newLink;
link.previous = newLink;
size++;
modCount++;
} else {
throw new IndexOutOfBoundsException();
}
}
/**
* Adds the specified object at the end of this {@code LinkedList}.
*
* @param object
* the object to add.
* @return always true
*/
@Override
public boolean add(E object) {
// Cannot call addLast() as subclasses can override
Link<E> oldLast = voidLink.previous;
Link<E> newLink = new Link<E>(object, oldLast, voidLink);
voidLink.previous = newLink;
oldLast.next = newLink;
size++;
modCount++;
return true;
}
/**
* Inserts the objects in the specified collection at the specified location
* in this {@code LinkedList}. The objects are added in the order they are
* returned from the collection's iterator.
*
* @param location
* the index at which to insert.
* @param collection
* the collection of objects
* @return {@code true} if this {@code LinkedList} is modified,
* {@code false} otherwise.
* @throws ClassCastException
* if the class of an object is inappropriate for this list.
* @throws IllegalArgumentException
* if an object cannot be added to this list.
* @throws IndexOutOfBoundsException
* if {@code location < 0 || > size()}
*/
@Override
public boolean addAll(int location, Collection<? extends E> collection) {
if (location < 0 || location > size) {
throw new IndexOutOfBoundsException();
}
int adding = collection.size();
if (adding == 0) {
return false;
}
Collection<? extends E> elements = (collection == this) ?
new ArrayList<E>(collection) : collection;
Link<E> previous = voidLink;
if (location < (size / 2)) {
for (int i = 0; i < location; i++) {
previous = previous.next;
}
} else {
for (int i = size; i >= location; i--) {
previous = previous.previous;
}
}
Link<E> next = previous.next;
for (E e : elements) {
Link<E> newLink = new Link<E>(e, previous, null);
previous.next = newLink;
previous = newLink;
}
previous.next = next;
next.previous = previous;
size += adding;
modCount++;
return true;
}
/**
* Adds the objects in the specified Collection to this {@code LinkedList}.
*
* @param collection
* the collection of objects.
* @return {@code true} if this {@code LinkedList} is modified,
* {@code false} otherwise.
*/
@Override
public boolean addAll(Collection<? extends E> collection) {
int adding = collection.size();
if (adding == 0) {
return false;
}
Collection<? extends E> elements = (collection == this) ?
new ArrayList<E>(collection) : collection;
Link<E> previous = voidLink.previous;
for (E e : elements) {
Link<E> newLink = new Link<E>(e, previous, null);
previous.next = newLink;
previous = newLink;
}
previous.next = voidLink;
voidLink.previous = previous;
size += adding;
modCount++;
return true;
}
/**
* Adds the specified object at the beginning of this {@code LinkedList}.
*
* @param object
* the object to add.
*/
public void addFirst(E object) {
Link<E> oldFirst = voidLink.next;
Link<E> newLink = new Link<E>(object, voidLink, oldFirst);
voidLink.next = newLink;
oldFirst.previous = newLink;
size++;
modCount++;
}
/**
* Adds the specified object at the end of this {@code LinkedList}.
*
* @param object
* the object to add.
*/
public void addLast(E object) {
Link<E> oldLast = voidLink.previous;
Link<E> newLink = new Link<E>(object, oldLast, voidLink);
voidLink.previous = newLink;
oldLast.next = newLink;
size++;
modCount++;
}
/**
* Removes all elements from this {@code LinkedList}, leaving it empty.
*
* @see List#isEmpty
* @see #size
*/
@Override
public void clear() {
if (size > 0) {
size = 0;
voidLink.next = voidLink;
voidLink.previous = voidLink;
modCount++;
}
}
/**
* Returns a new {@code LinkedList} with the same elements and size as this
* {@code LinkedList}.
*
* @return a shallow copy of this {@code LinkedList}.
* @see java.lang.Cloneable
*/
@SuppressWarnings("unchecked")
@Override
public Object clone() {
try {
LinkedList<E> l = (LinkedList<E>) super.clone();
l.size = 0;
l.voidLink = new Link<E>(null, null, null);
l.voidLink.previous = l.voidLink;
l.voidLink.next = l.voidLink;
l.addAll(this);
return l;
} catch (CloneNotSupportedException e) {
return null;
}
}
/**
* Searches this {@code LinkedList} for the specified object.
*
* @param object
* the object to search for.
* @return {@code true} if {@code object} is an element of this
* {@code LinkedList}, {@code false} otherwise
*/
@Override
public boolean contains(Object object) {
Link<E> link = voidLink.next;
if (object != null) {
while (link != voidLink) {
if (object.equals(link.data)) {
return true;
}
link = link.next;
}
} else {
while (link != voidLink) {
if (link.data == null) {
return true;
}
link = link.next;
}
}
return false;
}
@Override
public E get(int location) {
if (0 <= location && location < size) {
Link<E> link = voidLink;
if (location < (size / 2)) {
for (int i = 0; i <= location; i++) {
link = link.next;
}
} else {
for (int i = size; i > location; i--) {
link = link.previous;
}
}
return link.data;
}
throw new IndexOutOfBoundsException();
}
/**
* Returns the first element in this {@code LinkedList}.
*
* @return the first element.
* @throws NoSuchElementException
* if this {@code LinkedList} is empty.
*/
public E getFirst() {
Link<E> first = voidLink.next;
if (first != voidLink) {
return first.data;
}
throw new NoSuchElementException();
}
/**
* Returns the last element in this {@code LinkedList}.
*
* @return the last element
* @throws NoSuchElementException
* if this {@code LinkedList} is empty
*/
public E getLast() {
Link<E> last = voidLink.previous;
if (last != voidLink) {
return last.data;
}
throw new NoSuchElementException();
}
@Override
public int indexOf(Object object) {
int pos = 0;
Link<E> link = voidLink.next;
if (object != null) {
while (link != voidLink) {
if (object.equals(link.data)) {
return pos;
}
link = link.next;
pos++;
}
} else {
while (link != voidLink) {
if (link.data == null) {
return pos;
}
link = link.next;
pos++;
}
}
return -1;
}
/**
* Searches this {@code LinkedList} for the specified object and returns the
* index of the last occurrence.
*
* @param object
* the object to search for
* @return the index of the last occurrence of the object, or -1 if it was
* not found.
*/
@Override
public int lastIndexOf(Object object) {
int pos = size;
Link<E> link = voidLink.previous;
if (object != null) {
while (link != voidLink) {
pos--;
if (object.equals(link.data)) {
return pos;
}
link = link.previous;
}
} else {
while (link != voidLink) {
pos--;
if (link.data == null) {
return pos;
}
link = link.previous;
}
}
return -1;
}
/**
* Returns a ListIterator on the elements of this {@code LinkedList}. The
* elements are iterated in the same order that they occur in the
* {@code LinkedList}. The iteration starts at the specified location.
*
* @param location
* the index at which to start the iteration
* @return a ListIterator on the elements of this {@code LinkedList}
* @throws IndexOutOfBoundsException
* if {@code location < 0 || >= size()}
* @see ListIterator
*/
@Override
public ListIterator<E> listIterator(int location) {
return new LinkIterator<E>(this, location);
}
/**
* Removes the object at the specified location from this {@code LinkedList}.
*
* @param location
* the index of the object to remove
* @return the removed object
* @throws IndexOutOfBoundsException
* if {@code location < 0 || >= size()}
*/
@Override
public E remove(int location) {
if (0 <= location && location < size) {
Link<E> link = voidLink;
if (location < (size / 2)) {
for (int i = 0; i <= location; i++) {
link = link.next;
}
} else {
for (int i = size; i > location; i--) {
link = link.previous;
}
}
Link<E> previous = link.previous;
Link<E> next = link.next;
previous.next = next;
next.previous = previous;
size--;
modCount++;
return link.data;
}
throw new IndexOutOfBoundsException();
}
@Override
public boolean remove(Object object) {
Link<E> link = voidLink.next;
if (object != null) {
while (link != voidLink && !object.equals(link.data)) {
link = link.next;
}
} else {
while (link != voidLink && link.data != null) {
link = link.next;
}
}
if (link == voidLink) {
return false;
}
Link<E> next = link.next;
Link<E> previous = link.previous;
previous.next = next;
next.previous = previous;
size--;
modCount++;
return true;
}
/**
* Removes the first object from this {@code LinkedList}.
*
* @return the removed object.
* @throws NoSuchElementException
* if this {@code LinkedList} is empty.
*/
public E removeFirst() {
Link<E> first = voidLink.next;
if (first != voidLink) {
Link<E> next = first.next;
voidLink.next = next;
next.previous = voidLink;
size--;
modCount++;
return first.data;
}
throw new NoSuchElementException();
}
/**
* Removes the last object from this {@code LinkedList}.
*
* @return the removed object.
* @throws NoSuchElementException
* if this {@code LinkedList} is empty.
*/
public E removeLast() {
Link<E> last = voidLink.previous;
if (last != voidLink) {
Link<E> previous = last.previous;
voidLink.previous = previous;
previous.next = voidLink;
size--;
modCount++;
return last.data;
}
throw new NoSuchElementException();
}
/**
* Replaces the element at the specified location in this {@code LinkedList}
* with the specified object.
*
* @param location
* the index at which to put the specified object.
* @param object
* the object to add.
* @return the previous element at the index.
* @throws ClassCastException
* if the class of an object is inappropriate for this list.
* @throws IllegalArgumentException
* if an object cannot be added to this list.
* @throws IndexOutOfBoundsException
* if {@code location < 0 || >= size()}
*/
@Override
public E set(int location, E object) {
if (0 <= location && location < size) {
Link<E> link = voidLink;
if (location < (size / 2)) {
for (int i = 0; i <= location; i++) {
link = link.next;
}
} else {
for (int i = size; i > location; i--) {
link = link.previous;
}
}
E result = link.data;
link.data = object;
return result;
}
throw new IndexOutOfBoundsException();
}
/**
* Returns the number of elements in this {@code LinkedList}.
*
* @return the number of elements in this {@code LinkedList}.
*/
@Override
public int size() {
return size;
}
public boolean offer(E o) {
add(o);
return true;
}
public E poll() {
return size == 0 ? null : removeFirst();
}
public E remove() {
return removeFirst();
}
public E peek() {
Link<E> first = voidLink.next;
return first == voidLink ? null : first.data;
}
public E element() {
return getFirst();
}
/**
* Returns a new array containing all elements contained in this
* {@code LinkedList}.
*
* @return an array of the elements from this {@code LinkedList}.
*/
@Override
public Object[] toArray() {
int index = 0;
Object[] contents = new Object[size];
Link<E> link = voidLink.next;
while (link != voidLink) {
contents[index++] = link.data;
link = link.next;
}
return contents;
}
/**
* Returns an array containing all elements contained in this
* {@code LinkedList}. If the specified array is large enough to hold the
* elements, the specified array is used, otherwise an array of the same
* type is created. If the specified array is used and is larger than this
* {@code LinkedList}, the array element following the collection elements
* is set to null.
*
* @param contents
* the array.
* @return an array of the elements from this {@code LinkedList}.
* @throws ArrayStoreException
* if the type of an element in this {@code LinkedList} cannot
* be stored in the type of the specified array.
*/
@Override
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] contents) {
int index = 0;
if (size > contents.length) {
Class<?> ct = contents.getClass().getComponentType();
contents = (T[]) Array.newInstance(ct, size);
}
Link<E> link = voidLink.next;
while (link != voidLink) {
contents[index++] = (T) link.data;
link = link.next;
}
if (index < contents.length) {
contents[index] = null;
}
return contents;
}
public void concatenate(LinkedList<E> list) {
if (list.size != 0) { // if other list is not empty
// link last link from this with first one from other
voidLink.previous.next = list.voidLink.next;
list.voidLink.next.previous = voidLink.previous;
// link end of the other list with tail from this one
voidLink.previous = list.voidLink.previous;
list.voidLink.previous.next = voidLink;
// increase size and update modCount
size += list.size;
++modCount;
}
// detach links from appended list, update its size and modCount
list.voidLink.previous = list.voidLink.next = list.voidLink;
list.size = 0;
++list.modCount;
}
// Deque operations
/**
* Inserts the specified element at the front of this list.
*
* @param e the element to insert
* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
*/
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 <tt>true</tt> (as specified by {@link Deque#offerLast})
*/
public boolean offerLast(E e) {
addLast(e);
return true;
}
/**
* Retrieves, but does not remove, the first element of this list,
* or returns <tt>null</tt> if this list is empty.
*
* @return the first element of this list, or <tt>null</tt>
* if this list is empty
*/
public E peekFirst() {
if (size == 0)
return null;
return getFirst();
}
/**
* Retrieves, but does not remove, the last element of this list,
* or returns <tt>null</tt> if this list is empty.
*
* @return the last element of this list, or <tt>null</tt>
* if this list is empty
*/
public E peekLast() {
if (size == 0)
return null;
return getLast();
}
/**
* Retrieves and removes the first element of this list,
* or returns <tt>null</tt> if this list is empty.
*
* @return the first element of this list, or <tt>null</tt> if
* this list is empty
*/
public E pollFirst() {
if (size == 0)
return null;
return removeFirst();
}
/**
* Retrieves and removes the last element of this list,
* or returns <tt>null</tt> if this list is empty.
*
* @return the last element of this list, or <tt>null</tt> if
* this list is empty
*/
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.
*
* <p>This method is equivalent to {@link #addFirst}.
*
* @param e the element to push
*/
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.
*
* <p>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
*/
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 <tt>true</tt> if the list contained the specified element
*/
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 <tt>true</tt> if the list contained the specified element
*/
public boolean removeLastOccurrence(Object object) {
Link<E> link = voidLink.previous;
if (object != null) {
while (link != voidLink && !object.equals(link.data)) {
link = link.previous;
}
} else {
while (link != voidLink && link.data != null) {
link = link.previous;
}
}
if (link == voidLink) {
return false;
}
Link<E> next = link.next;
Link<E> previous = link.previous;
previous.next = next;
next.previous = previous;
size--;
modCount++;
return true;
}
@Override
public Iterator<E> descendingIterator() {
return new DescendingIterator<E>(this);
}
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeInt(size);
Iterator<E> it = iterator();
while (it.hasNext()) {
stream.writeObject(it.next());
}
}
@SuppressWarnings("unchecked")
private void readObject(ObjectInputStream stream) throws IOException,
ClassNotFoundException {
stream.defaultReadObject();
size = stream.readInt();
voidLink = new Link<E>(null, null, null);
Link<E> link = voidLink;
for (int i = size; --i >= 0;) {
Link<E> nextLink = new Link<E>((E) stream.readObject(), link, null);
link.next = nextLink;
link = nextLink;
}
link.next = voidLink;
voidLink.previous = link;
}
}