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The Commons Collections TreeList.java source code
/*
* 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.apache.commons.collections.list;
import java.util.AbstractList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import org.apache.commons.collections.OrderedIterator;
/**
* A <code>List implementation that is optimised for fast insertions and
* removals at any index in the list.
* <p>
* This list implementation utilises a tree structure internally to ensure that
* all insertions and removals are O(log n). This provides much faster performance
* than both an <code>ArrayList and a LinkedList where elements
* are inserted and removed repeatedly from anywhere in the list.
* <p>
* The following relative performance statistics are indicative of this class:
* <pre>
* get add insert iterate remove
* TreeList 3 5 1 2 1
* ArrayList 1 1 40 1 40
* LinkedList 5800 1 350 2 325
* </pre>
* <code>ArrayList is a good general purpose list implementation.
* It is faster than <code>TreeList for most operations except inserting
* and removing in the middle of the list. <code>ArrayList also uses less
* memory as <code>TreeList uses one object per entry.
* <p>
* <code>LinkedList is rarely a good choice of implementation.
* <code>TreeList is almost always a good replacement for it, although it
* does use sligtly more memory.
*
* @since Commons Collections 3.1
* @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
*
* @author Joerg Schmuecker
* @author Stephen Colebourne
*/
public class TreeList extends AbstractList {
// add; toArray; iterator; insert; get; indexOf; remove
// TreeList = 1260;7360;3080; 160; 170;3400; 170;
// ArrayList = 220;1480;1760; 6870; 50;1540; 7200;
// LinkedList = 270;7360;3350;55860;290720;2910;55200;
/** The root node in the AVL tree */
private AVLNode root;
/** The current size of the list */
private int size;
//-----------------------------------------------------------------------
/**
* Constructs a new empty list.
*/
public TreeList() {
super();
}
/**
* Constructs a new empty list that copies the specified list.
*
* @param coll the collection to copy
* @throws NullPointerException if the collection is null
*/
public TreeList(Collection coll) {
super();
addAll(coll);
}
//-----------------------------------------------------------------------
/**
* Gets the element at the specified index.
*
* @param index the index to retrieve
* @return the element at the specified index
*/
public Object get(int index) {
checkInterval(index, 0, size() - 1);
return root.get(index).getValue();
}
/**
* Gets the current size of the list.
*
* @return the current size
*/
public int size() {
return size;
}
/**
* Gets an iterator over the list.
*
* @return an iterator over the list
*/
public Iterator iterator() {
// override to go 75% faster
return listIterator(0);
}
/**
* Gets a ListIterator over the list.
*
* @return the new iterator
*/
public ListIterator listIterator() {
// override to go 75% faster
return listIterator(0);
}
/**
* Gets a ListIterator over the list.
*
* @param fromIndex the index to start from
* @return the new iterator
*/
public ListIterator listIterator(int fromIndex) {
// override to go 75% faster
// cannot use EmptyIterator as iterator.add() must work
checkInterval(fromIndex, 0, size());
return new TreeListIterator(this, fromIndex);
}
/**
* Searches for the index of an object in the list.
*
* @return the index of the object, -1 if not found
*/
public int indexOf(Object object) {
// override to go 75% faster
if (root == null) {
return -1;
}
return root.indexOf(object, root.relativePosition);
}
/**
* Searches for the presence of an object in the list.
*
* @return true if the object is found
*/
public boolean contains(Object object) {
return (indexOf(object) >= 0);
}
/**
* Converts the list into an array.
*
* @return the list as an array
*/
public Object[] toArray() {
// override to go 20% faster
Object[] array = new Object[size()];
if (root != null) {
root.toArray(array, root.relativePosition);
}
return array;
}
//-----------------------------------------------------------------------
/**
* Adds a new element to the list.
*
* @param index the index to add before
* @param obj the element to add
*/
public void add(int index, Object obj) {
modCount++;
checkInterval(index, 0, size());
if (root == null) {
root = new AVLNode(index, obj, null, null);
} else {
root = root.insert(index, obj);
}
size++;
}
/**
* Sets the element at the specified index.
*
* @param index the index to set
* @param obj the object to store at the specified index
* @return the previous object at that index
* @throws IndexOutOfBoundsException if the index is invalid
*/
public Object set(int index, Object obj) {
checkInterval(index, 0, size() - 1);
AVLNode node = root.get(index);
Object result = node.value;
node.setValue(obj);
return result;
}
/**
* Removes the element at the specified index.
*
* @param index the index to remove
* @return the previous object at that index
*/
public Object remove(int index) {
modCount++;
checkInterval(index, 0, size() - 1);
Object result = get(index);
root = root.remove(index);
size--;
return result;
}
/**
* Clears the list, removing all entries.
*/
public void clear() {
modCount++;
root = null;
size = 0;
}
//-----------------------------------------------------------------------
/**
* Checks whether the index is valid.
*
* @param index the index to check
* @param startIndex the first allowed index
* @param endIndex the last allowed index
* @throws IndexOutOfBoundsException if the index is invalid
*/
private void checkInterval(int index, int startIndex, int endIndex) {
if (index < startIndex || index > endIndex) {
throw new IndexOutOfBoundsException("Invalid index:" + index + ", size=" + size());
}
}
//-----------------------------------------------------------------------
/**
* Implements an AVLNode which keeps the offset updated.
* <p>
* This node contains the real work.
* TreeList is just there to implement {@link java.util.List}.
* The nodes don't know the index of the object they are holding. They
* do know however their position relative to their parent node.
* This allows to calculate the index of a node while traversing the tree.
* <p>
* The Faedelung calculation stores a flag for both the left and right child
* to indicate if they are a child (false) or a link as in linked list (true).
*/
static class AVLNode {
/** The left child node or the predecessor if {@link #leftIsPrevious}.*/
private AVLNode left;
/** Flag indicating that left reference is not a subtree but the predecessor. */
private boolean leftIsPrevious;
/** The right child node or the successor if {@link #rightIsNext}. */
private AVLNode right;
/** Flag indicating that right reference is not a subtree but the successor. */
private boolean rightIsNext;
/** How many levels of left/right are below this one. */
private int height;
/** The relative position, root holds absolute position. */
private int relativePosition;
/** The stored element. */
private Object value;
/**
* Constructs a new node with a relative position.
*
* @param relativePosition the relative position of the node
* @param obj the value for the ndoe
* @param rightFollower the node with the value following this one
* @param leftFollower the node with the value leading this one
*/
private AVLNode(int relativePosition, Object obj, AVLNode rightFollower, AVLNode leftFollower) {
this.relativePosition = relativePosition;
value = obj;
rightIsNext = true;
leftIsPrevious = true;
right = rightFollower;
left = leftFollower;
}
/**
* Gets the value.
*
* @return the value of this node
*/
Object getValue() {
return value;
}
/**
* Sets the value.
*
* @param obj the value to store
*/
void setValue(Object obj) {
this.value = obj;
}
/**
* Locate the element with the given index relative to the
* offset of the parent of this node.
*/
AVLNode get(int index) {
int indexRelativeToMe = index - relativePosition;
if (indexRelativeToMe == 0) {
return this;
}
AVLNode nextNode = ((indexRelativeToMe < 0) ? getLeftSubTree() : getRightSubTree());
if (nextNode == null) {
return null;
}
return nextNode.get(indexRelativeToMe);
}
/**
* Locate the index that contains the specified object.
*/
int indexOf(Object object, int index) {
if (getLeftSubTree() != null) {
int result = left.indexOf(object, index + left.relativePosition);
if (result != -1) {
return result;
}
}
if (value == null ? value == object : value.equals(object)) {
return index;
}
if (getRightSubTree() != null) {
return right.indexOf(object, index + right.relativePosition);
}
return -1;
}
/**
* Stores the node and its children into the array specified.
*
* @param array the array to be filled
* @param index the index of this node
*/
void toArray(Object[] array, int index) {
array[index] = value;
if (getLeftSubTree() != null) {
left.toArray(array, index + left.relativePosition);
}
if (getRightSubTree() != null) {
right.toArray(array, index + right.relativePosition);
}
}
/**
* Gets the next node in the list after this one.
*
* @return the next node
*/
AVLNode next() {
if (rightIsNext || right == null) {
return right;
}
return right.min();
}
/**
* Gets the node in the list before this one.
*
* @return the previous node
*/
AVLNode previous() {
if (leftIsPrevious || left == null) {
return left;
}
return left.max();
}
/**
* Inserts a node at the position index.
*
* @param index is the index of the position relative to the position of
* the parent node.
* @param obj is the object to be stored in the position.
*/
AVLNode insert(int index, Object obj) {
int indexRelativeToMe = index - relativePosition;
if (indexRelativeToMe <= 0) {
return insertOnLeft(indexRelativeToMe, obj);
} else {
return insertOnRight(indexRelativeToMe, obj);
}
}
private AVLNode insertOnLeft(int indexRelativeToMe, Object obj) {
AVLNode ret = this;
if (getLeftSubTree() == null) {
setLeft(new AVLNode(-1, obj, this, left), null);
} else {
setLeft(left.insert(indexRelativeToMe, obj), null);
}
if (relativePosition >= 0) {
relativePosition++;
}
ret = balance();
recalcHeight();
return ret;
}
private AVLNode insertOnRight(int indexRelativeToMe, Object obj) {
AVLNode ret = this;
if (getRightSubTree() == null) {
setRight(new AVLNode(+1, obj, right, this), null);
} else {
setRight(right.insert(indexRelativeToMe, obj), null);
}
if (relativePosition < 0) {
relativePosition--;
}
ret = balance();
recalcHeight();
return ret;
}
//-----------------------------------------------------------------------
/**
* Gets the left node, returning null if its a faedelung.
*/
private AVLNode getLeftSubTree() {
return (leftIsPrevious ? null : left);
}
/**
* Gets the right node, returning null if its a faedelung.
*/
private AVLNode getRightSubTree() {
return (rightIsNext ? null : right);
}
/**
* Gets the rightmost child of this node.
*
* @return the rightmost child (greatest index)
*/
private AVLNode max() {
return (getRightSubTree() == null) ? this : right.max();
}
/**
* Gets the leftmost child of this node.
*
* @return the leftmost child (smallest index)
*/
private AVLNode min() {
return (getLeftSubTree() == null) ? this : left.min();
}
/**
* Removes the node at a given position.
*
* @param index is the index of the element to be removed relative to the position of
* the parent node of the current node.
*/
AVLNode remove(int index) {
int indexRelativeToMe = index - relativePosition;
if (indexRelativeToMe == 0) {
return removeSelf();
}
if (indexRelativeToMe > 0) {
setRight(right.remove(indexRelativeToMe), right.right);
if (relativePosition < 0) {
relativePosition++;
}
} else {
setLeft(left.remove(indexRelativeToMe), left.left);
if (relativePosition > 0) {
relativePosition--;
}
}
recalcHeight();
return balance();
}
private AVLNode removeMax() {
if (getRightSubTree() == null) {
return removeSelf();
}
setRight(right.removeMax(), right.right);
if (relativePosition < 0) {
relativePosition++;
}
recalcHeight();
return balance();
}
private AVLNode removeMin() {
if (getLeftSubTree() == null) {
return removeSelf();
}
setLeft(left.removeMin(), left.left);
if (relativePosition > 0) {
relativePosition--;
}
recalcHeight();
return balance();
}
/**
* Removes this node from the tree.
*
* @return the node that replaces this one in the parent
*/
private AVLNode removeSelf() {
if (getRightSubTree() == null && getLeftSubTree() == null) {
return null;
}
if (getRightSubTree() == null) {
if (relativePosition > 0) {
left.relativePosition += relativePosition + (relativePosition > 0 ? 0 : 1);
}
left.max().setRight(null, right);
return left;
}
if (getLeftSubTree() == null) {
right.relativePosition += relativePosition - (relativePosition < 0 ? 0 : 1);
right.min().setLeft(null, left);
return right;
}
if (heightRightMinusLeft() > 0) {
// more on the right, so delete from the right
AVLNode rightMin = right.min();
value = rightMin.value;
if (leftIsPrevious) {
left = rightMin.left;
}
right = right.removeMin();
if (relativePosition < 0) {
relativePosition++;
}
} else {
// more on the left or equal, so delete from the left
AVLNode leftMax = left.max();
value = leftMax.value;
if (rightIsNext) {
right = leftMax.right;
}
AVLNode leftPrevious = left.left;
left = left.removeMax();
if (left == null) {
// special case where left that was deleted was a double link
// only occurs when height difference is equal
left = leftPrevious;
leftIsPrevious = true;
}
if (relativePosition > 0) {
relativePosition--;
}
}
recalcHeight();
return this;
}
//-----------------------------------------------------------------------
/**
* Balances according to the AVL algorithm.
*/
private AVLNode balance() {
switch (heightRightMinusLeft()) {
case 1 :
case 0 :
case -1 :
return this;
case -2 :
if (left.heightRightMinusLeft() > 0) {
setLeft(left.rotateLeft(), null);
}
return rotateRight();
case 2 :
if (right.heightRightMinusLeft() < 0) {
setRight(right.rotateRight(), null);
}
return rotateLeft();
default :
throw new RuntimeException("tree inconsistent!");
}
}
/**
* Gets the relative position.
*/
private int getOffset(AVLNode node) {
if (node == null) {
return 0;
}
return node.relativePosition;
}
/**
* Sets the relative position.
*/
private int setOffset(AVLNode node, int newOffest) {
if (node == null) {
return 0;
}
int oldOffset = getOffset(node);
node.relativePosition = newOffest;
return oldOffset;
}
/**
* Sets the height by calculation.
*/
private void recalcHeight() {
height = Math.max(
getLeftSubTree() == null ? -1 : getLeftSubTree().height,
getRightSubTree() == null ? -1 : getRightSubTree().height) + 1;
}
/**
* Returns the height of the node or -1 if the node is null.
*/
private int getHeight(AVLNode node) {
return (node == null ? -1 : node.height);
}
/**
* Returns the height difference right - left
*/
private int heightRightMinusLeft() {
return getHeight(getRightSubTree()) - getHeight(getLeftSubTree());
}
private AVLNode rotateLeft() {
AVLNode newTop = right; // can't be faedelung!
AVLNode movedNode = getRightSubTree().getLeftSubTree();
int newTopPosition = relativePosition + getOffset(newTop);
int myNewPosition = -newTop.relativePosition;
int movedPosition = getOffset(newTop) + getOffset(movedNode);
setRight(movedNode, newTop);
newTop.setLeft(this, null);
setOffset(newTop, newTopPosition);
setOffset(this, myNewPosition);
setOffset(movedNode, movedPosition);
return newTop;
}
private AVLNode rotateRight() {
AVLNode newTop = left; // can't be faedelung
AVLNode movedNode = getLeftSubTree().getRightSubTree();
int newTopPosition = relativePosition + getOffset(newTop);
int myNewPosition = -newTop.relativePosition;
int movedPosition = getOffset(newTop) + getOffset(movedNode);
setLeft(movedNode, newTop);
newTop.setRight(this, null);
setOffset(newTop, newTopPosition);
setOffset(this, myNewPosition);
setOffset(movedNode, movedPosition);
return newTop;
}
/**
* Sets the left field to the node, or the previous node if that is null
*
* @param node the new left subtree node
* @param previous the previous node in the linked list
*/
private void setLeft(AVLNode node, AVLNode previous) {
leftIsPrevious = (node == null);
left = (leftIsPrevious ? previous : node);
recalcHeight();
}
/**
* Sets the right field to the node, or the next node if that is null
*
* @param node the new left subtree node
* @param next the next node in the linked list
*/
private void setRight(AVLNode node, AVLNode next) {
rightIsNext = (node == null);
right = (rightIsNext ? next : node);
recalcHeight();
}
// private void checkFaedelung() {
// AVLNode maxNode = left.max();
// if (!maxNode.rightIsFaedelung || maxNode.right != this) {
// throw new RuntimeException(maxNode + " should right-faedel to " + this);
// }
// AVLNode minNode = right.min();
// if (!minNode.leftIsFaedelung || minNode.left != this) {
// throw new RuntimeException(maxNode + " should left-faedel to " + this);
// }
// }
//
// private int checkTreeDepth() {
// int hright = (getRightSubTree() == null ? -1 : getRightSubTree().checkTreeDepth());
// // System.out.print("checkTreeDepth");
// // System.out.print(this);
// // System.out.print(" left: ");
// // System.out.print(_left);
// // System.out.print(" right: ");
// // System.out.println(_right);
//
// int hleft = (left == null ? -1 : left.checkTreeDepth());
// if (height != Math.max(hright, hleft) + 1) {
// throw new RuntimeException(
// "height should be max" + hleft + "," + hright + " but is " + height);
// }
// return height;
// }
//
// private int checkLeftSubNode() {
// if (getLeftSubTree() == null) {
// return 0;
// }
// int count = 1 + left.checkRightSubNode();
// if (left.relativePosition != -count) {
// throw new RuntimeException();
// }
// return count + left.checkLeftSubNode();
// }
//
// private int checkRightSubNode() {
// AVLNode right = getRightSubTree();
// if (right == null) {
// return 0;
// }
// int count = 1;
// count += right.checkLeftSubNode();
// if (right.relativePosition != count) {
// throw new RuntimeException();
// }
// return count + right.checkRightSubNode();
// }
/**
* Used for debugging.
*/
public String toString() {
return "AVLNode(" + relativePosition + "," + (left != null) + "," + value +
"," + (getRightSubTree() != null) + ", faedelung " + rightIsNext + " )";
}
}
/**
* A list iterator over the linked list.
*/
static class TreeListIterator implements ListIterator, OrderedIterator {
/** The parent list */
protected final TreeList parent;
/**
* Cache of the next node that will be returned by {@link #next()}.
*/
protected AVLNode next;
/**
* The index of the next node to be returned.
*/
protected int nextIndex;
/**
* Cache of the last node that was returned by {@link #next()}
* or {@link #previous()}.
*/
protected AVLNode current;
/**
* The index of the last node that was returned.
*/
protected int currentIndex;
/**
* The modification count that the list is expected to have. If the list
* doesn't have this count, then a
* {@link java.util.ConcurrentModificationException} may be thrown by
* the operations.
*/
protected int expectedModCount;
/**
* Create a ListIterator for a list.
*
* @param parent the parent list
* @param fromIndex the index to start at
*/
protected TreeListIterator(TreeList parent, int fromIndex) throws IndexOutOfBoundsException {
super();
this.parent = parent;
this.expectedModCount = parent.modCount;
this.next = (parent.root == null ? null : parent.root.get(fromIndex));
this.nextIndex = fromIndex;
this.currentIndex = -1;
}
/**
* Checks the modification count of the list is the value that this
* object expects.
*
* @throws ConcurrentModificationException If the list's modification
* count isn't the value that was expected.
*/
protected void checkModCount() {
if (parent.modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
public boolean hasNext() {
return (nextIndex < parent.size());
}
public Object next() {
checkModCount();
if (!hasNext()) {
throw new NoSuchElementException("No element at index " + nextIndex + ".");
}
if (next == null) {
next = parent.root.get(nextIndex);
}
Object value = next.getValue();
current = next;
currentIndex = nextIndex++;
next = next.next();
return value;
}
public boolean hasPrevious() {
return (nextIndex > 0);
}
public Object previous() {
checkModCount();
if (!hasPrevious()) {
throw new NoSuchElementException("Already at start of list.");
}
if (next == null) {
next = parent.root.get(nextIndex - 1);
} else {
next = next.previous();
}
Object value = next.getValue();
current = next;
currentIndex = --nextIndex;
return value;
}
public int nextIndex() {
return nextIndex;
}
public int previousIndex() {
return nextIndex() - 1;
}
public void remove() {
checkModCount();
if (currentIndex == -1) {
throw new IllegalStateException();
}
if (nextIndex == currentIndex) {
// remove() following previous()
next = next.next();
parent.remove(currentIndex);
} else {
// remove() following next()
parent.remove(currentIndex);
nextIndex--;
}
current = null;
currentIndex = -1;
expectedModCount++;
}
public void set(Object obj) {
checkModCount();
if (current == null) {
throw new IllegalStateException();
}
current.setValue(obj);
}
public void add(Object obj) {
checkModCount();
parent.add(nextIndex, obj);
current = null;
currentIndex = -1;
nextIndex++;
expectedModCount++;
}
}
}
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