Commons Collections example source code file (CursorableLinkedList.java)
The Commons Collections CursorableLinkedList.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;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.lang.ref.WeakReference;
/**
* A doubly-linked list implementation of the {@link List} interface,
* supporting a {@link ListIterator} that allows concurrent modifications
* to the underlying list.
* <p>
* Implements all of the optional {@link List} operations, the
* stack/queue/dequeue operations available in {@link java.util.LinkedList}
* and supports a {@link ListIterator} that allows concurrent modifications
* to the underlying list (see {@link #cursor}).
* <p>
* <b>Note that this implementation is not synchronized.
*
* @deprecated Use new version in list subpackage, which has been rewritten
* and now returns the cursor from the listIterator method. Will be removed in v4.0
* @see java.util.LinkedList
* @since Commons Collections 1.0
* @version $Revision: 647116 $ $Date: 2008-04-11 12:23:08 +0100 (Fri, 11 Apr 2008) $
*
* @author Rodney Waldhoff
* @author Janek Bogucki
* @author Simon Kitching
*/
public class CursorableLinkedList implements List, Serializable {
/** Ensure serialization compatibility */
private static final long serialVersionUID = 8836393098519411393L;
//--- public methods ---------------------------------------------
/**
* Appends the specified element to the end of this list.
*
* @param o element to be appended to this list.
* @return <tt>true
*/
public boolean add(Object o) {
insertListable(_head.prev(),null,o);
return true;
}
/**
* 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 ClassCastException if the class of the specified element
* prevents it from being added to this list.
* @throws IllegalArgumentException if some aspect of the specified
* element prevents it from being added to this list.
* @throws IndexOutOfBoundsException if the index is out of range
* (index < 0 || index > size()).
*/
public void add(int index, Object element) {
if(index == _size) {
add(element);
} else {
if(index < 0 || index > _size) {
throw new IndexOutOfBoundsException(String.valueOf(index) + " < 0 or " + String.valueOf(index) + " > " + _size);
}
Listable succ = (isEmpty() ? null : getListableAt(index));
Listable pred = (null == succ ? null : succ.prev());
insertListable(pred,succ,element);
}
}
/**
* 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
* {@link Collection}'s {@link Iterator}. The behavior of this operation is
* unspecified if the specified collection is modified while
* the operation is in progress. (Note that this will occur if the
* specified collection is this list, and it's nonempty.)
*
* @param c collection whose elements are to be added to this list.
* @return <tt>true if this list changed as a result of the call.
*
* @throws ClassCastException if the class of an element in the specified
* collection prevents it from being added to this list.
* @throws IllegalArgumentException if some aspect of an element in the
* specified collection prevents it from being added to this
* list.
*/
public boolean addAll(Collection c) {
if(c.isEmpty()) {
return false;
}
Iterator it = c.iterator();
while(it.hasNext()) {
insertListable(_head.prev(),null,it.next());
}
return true;
}
/**
* Inserts all of the elements in the specified collection into this
* list 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 this
* list in the order that they are returned by the specified
* {@link Collection}'s {@link Iterator}. The behavior of this operation is
* unspecified if the specified collection is modified while the
* operation is in progress. (Note that this will occur if the specified
* collection is this list, and it's nonempty.)
*
* @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 if this list changed as a result of the call.
*
* @throws ClassCastException if the class of one of elements of the
* specified collection prevents it from being added to this
* list.
* @throws IllegalArgumentException if some aspect of one of elements of
* the specified collection prevents it from being added to
* this list.
* @throws IndexOutOfBoundsException if the index is out of range (index
* < 0 || index > size()).
*/
public boolean addAll(int index, Collection c) {
if(c.isEmpty()) {
return false;
} else if(_size == index || _size == 0) {
return addAll(c);
} else {
Listable succ = getListableAt(index);
Listable pred = (null == succ) ? null : succ.prev();
Iterator it = c.iterator();
while(it.hasNext()) {
pred = insertListable(pred,succ,it.next());
}
return true;
}
}
/**
* Inserts the specified element at the beginning of this list.
* (Equivalent to {@link #add(int,java.lang.Object) <tt>add(0,o)}).
*
* @param o element to be prepended to this list.
* @return <tt>true
*/
public boolean addFirst(Object o) {
insertListable(null,_head.next(),o);
return true;
}
/**
* Inserts the specified element at the end of this list.
* (Equivalent to {@link #add(java.lang.Object)}).
*
* @param o element to be appended to this list.
* @return <tt>true
*/
public boolean addLast(Object o) {
insertListable(_head.prev(),null,o);
return true;
}
/**
* Removes all of the elements from this list. This
* list will be empty after this call returns (unless
* it throws an exception).
*/
public void clear() {
/*
// this is the quick way, but would force us
// to break all the cursors
_modCount++;
_head.setNext(null);
_head.setPrev(null);
_size = 0;
*/
Iterator it = iterator();
while(it.hasNext()) {
it.next();
it.remove();
}
}
/**
* Returns <tt>true if this list contains the specified element.
* More formally, returns <tt>true if and only if this list contains
* at least one element <tt>e such that
* <tt>(o==null ? e==null : o.equals(e)).
*
* @param o element whose presence in this list is to be tested.
* @return <tt>true if this list contains the specified element.
*/
public boolean contains(Object o) {
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
if((null == o && null == elt.value()) ||
(o != null && o.equals(elt.value()))) {
return true;
}
}
return false;
}
/**
* Returns <tt>true if this list contains all of the elements of the
* specified collection.
*
* @param c collection to be checked for containment in this list.
* @return <tt>true if this list contains all of the elements of the
* specified collection.
*/
public boolean containsAll(Collection c) {
Iterator it = c.iterator();
while(it.hasNext()) {
if(!this.contains(it.next())) {
return false;
}
}
return true;
}
/**
* Returns a {@link ListIterator} for iterating through the
* elements of this list. Unlike {@link #iterator}, a cursor
* is not bothered by concurrent modifications to the
* underlying list.
* <p>
* Specifically, when elements are added to the list before or
* after the cursor, the cursor simply picks them up automatically.
* When the "current" (i.e., last returned by {@link ListIterator#next}
* or {@link ListIterator#previous}) element of the list is removed,
* the cursor automatically adjusts to the change (invalidating the
* last returned value--i.e., it cannot be removed).
* <p>
* Note that the returned {@link ListIterator} does not support the
* {@link ListIterator#nextIndex} and {@link ListIterator#previousIndex}
* methods (they throw {@link UnsupportedOperationException} when invoked.
* <p>
* Historical Note: In previous versions of this class, the object
* returned from this method was required to be explicitly closed. This
* is no longer necessary.
*
* @see #cursor(int)
* @see #listIterator
* @see CursorableLinkedList.Cursor
*/
public CursorableLinkedList.Cursor cursor() {
return new Cursor(0);
}
/**
* Returns a {@link ListIterator} for iterating through the
* elements of this list, initialized such that
* {@link ListIterator#next} will return the element at
* the specified index (if any) and {@link ListIterator#previous}
* will return the element immediately preceding it (if any).
* Unlike {@link #iterator}, a cursor
* is not bothered by concurrent modifications to the
* underlying list.
*
* @see #cursor
* @see #listIterator(int)
* @see CursorableLinkedList.Cursor
* @throws IndexOutOfBoundsException if the index is out of range (index
* < 0 || index > size()).
*/
public CursorableLinkedList.Cursor cursor(int i) {
return new Cursor(i);
}
/**
* Compares the specified object with this list for equality. Returns
* <tt>true if and only if the specified object is also a list, both
* lists have the same size, and all corresponding pairs of elements in
* the two lists are <i>equal. (Two elements e1 and
* <tt>e2 are equal if (e1==null ? e2==null :
* e1.equals(e2))</tt>.) In other words, two lists are defined to be
* equal if they contain the same elements in the same order. This
* definition ensures that the equals method works properly across
* different implementations of the <tt>List interface.
*
* @param o the object to be compared for equality with this list.
* @return <tt>true if the specified object is equal to this list.
*/
public boolean equals(Object o) {
if(o == this) {
return true;
} else if(!(o instanceof List)) {
return false;
}
Iterator it = ((List)o).listIterator();
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
if(!it.hasNext() || (null == elt.value() ? null != it.next() : !(elt.value().equals(it.next()))) ) {
return false;
}
}
return !it.hasNext();
}
/**
* 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 index is out of range (index
* < 0 || index >= size()).
*/
public Object get(int index) {
return getListableAt(index).value();
}
/**
* Returns the element at the beginning of this list.
*/
public Object getFirst() {
try {
return _head.next().value();
} catch(NullPointerException e) {
throw new NoSuchElementException();
}
}
/**
* Returns the element at the end of this list.
*/
public Object getLast() {
try {
return _head.prev().value();
} catch(NullPointerException e) {
throw new NoSuchElementException();
}
}
/**
* Returns the hash code value for this list. The hash code of a list
* is defined to be the result of the following calculation:
* <pre>
* hashCode = 1;
* Iterator i = list.iterator();
* while (i.hasNext()) {
* Object obj = i.next();
* hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode());
* }
* </pre>
* This ensures that <tt>list1.equals(list2) implies that
* <tt>list1.hashCode()==list2.hashCode() for any two lists,
* <tt>list1 and list2, as required by the general
* contract of <tt>Object.hashCode.
*
* @return the hash code value for this list.
* @see Object#hashCode()
* @see Object#equals(Object)
* @see #equals(Object)
*/
public int hashCode() {
int hash = 1;
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
hash = 31*hash + (null == elt.value() ? 0 : elt.value().hashCode());
}
return hash;
}
/**
* Returns the index in this list of the first occurrence of the specified
* element, or -1 if this list does not contain this element.
* More formally, returns the lowest index <tt>i such that
* <tt>(o==null ? get(i)==null : o.equals(get(i))),
* 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 this list does not contain this element.
*/
public int indexOf(Object o) {
int ndx = 0;
// perform the null check outside of the loop to save checking every
// single time through the loop.
if (null == o) {
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
if (null == elt.value()) {
return ndx;
}
ndx++;
}
} else {
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
if (o.equals(elt.value())) {
return ndx;
}
ndx++;
}
}
return -1;
}
/**
* Returns <tt>true if this list contains no elements.
* @return <tt>true if this list contains no elements.
*/
public boolean isEmpty() {
return(0 == _size);
}
/**
* Returns a fail-fast iterator.
* @see List#iterator
*/
public Iterator iterator() {
return listIterator(0);
}
/**
* Returns the index in this list of the last occurrence of the specified
* element, or -1 if this list does not contain this element.
* More formally, returns the highest index <tt>i such that
* <tt>(o==null ? get(i)==null : o.equals(get(i))),
* 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 this list does not contain this element.
*/
public int lastIndexOf(Object o) {
int ndx = _size-1;
// perform the null check outside of the loop to save checking every
// single time through the loop.
if (null == o) {
for(Listable elt = _head.prev(), past = null; null != elt && past != _head.next(); elt = (past = elt).prev()) {
if (null == elt.value()) {
return ndx;
}
ndx--;
}
} else {
for(Listable elt = _head.prev(), past = null; null != elt && past != _head.next(); elt = (past = elt).prev()) {
if (o.equals(elt.value())) {
return ndx;
}
ndx--;
}
}
return -1;
}
/**
* Returns a fail-fast ListIterator.
* @see List#listIterator
*/
public ListIterator listIterator() {
return listIterator(0);
}
/**
* Returns a fail-fast ListIterator.
* @see List#listIterator(int)
*/
public ListIterator listIterator(int index) {
if(index<0 || index > _size) {
throw new IndexOutOfBoundsException(index + " < 0 or > " + _size);
}
return new ListIter(index);
}
/**
* Removes the first occurrence in this list of the specified element.
* If this list does not contain the element, it is
* unchanged. More formally, removes the element with the lowest index i
* such that <tt>(o==null ? get(i)==null : o.equals(get(i))) (if
* such an element exists).
*
* @param o element to be removed from this list, if present.
* @return <tt>true if this list contained the specified element.
*/
public boolean remove(Object o) {
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
if(null == o && null == elt.value()) {
removeListable(elt);
return true;
} else if(o != null && o.equals(elt.value())) {
removeListable(elt);
return true;
}
}
return false;
}
/**
* Removes the element at the specified position in this list (optional
* operation). 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 index is out of range (index
* < 0 || index >= size()).
*/
public Object remove(int index) {
Listable elt = getListableAt(index);
Object ret = elt.value();
removeListable(elt);
return ret;
}
/**
* Removes from this list all the elements that are contained in the
* specified collection.
*
* @param c collection that defines which elements will be removed from
* this list.
* @return <tt>true if this list changed as a result of the call.
*/
public boolean removeAll(Collection c) {
if(0 == c.size() || 0 == _size) {
return false;
} else {
boolean changed = false;
Iterator it = iterator();
while(it.hasNext()) {
if(c.contains(it.next())) {
it.remove();
changed = true;
}
}
return changed;
}
}
/**
* Removes the first element of this list, if any.
*/
public Object removeFirst() {
if(_head.next() != null) {
Object val = _head.next().value();
removeListable(_head.next());
return val;
} else {
throw new NoSuchElementException();
}
}
/**
* Removes the last element of this list, if any.
*/
public Object removeLast() {
if(_head.prev() != null) {
Object val = _head.prev().value();
removeListable(_head.prev());
return val;
} else {
throw new NoSuchElementException();
}
}
/**
* Retains only the elements in this list that are contained in the
* specified collection. In other words, removes
* from this list all the elements that are not contained in the specified
* collection.
*
* @param c collection that defines which elements this set will retain.
*
* @return <tt>true if this list changed as a result of the call.
*/
public boolean retainAll(Collection c) {
boolean changed = false;
Iterator it = iterator();
while(it.hasNext()) {
if(!c.contains(it.next())) {
it.remove();
changed = true;
}
}
return changed;
}
/**
* 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 ClassCastException if the class of the specified element
* prevents it from being added to this list.
* @throws IllegalArgumentException if some aspect of the specified
* element prevents it from being added to this list.
* @throws IndexOutOfBoundsException if the index is out of range
* (index < 0 || index >= size()).
*/
public Object set(int index, Object element) {
Listable elt = getListableAt(index);
Object val = elt.setValue(element);
broadcastListableChanged(elt);
return val;
}
/**
* Returns the number of elements in this list.
* @return the number of elements in this list.
*/
public int size() {
return _size;
}
/**
* Returns an array containing all of the elements in this list in proper
* sequence. Obeys the general contract of the {@link Collection#toArray} method.
*
* @return an array containing all of the elements in this list in proper
* sequence.
*/
public Object[] toArray() {
Object[] array = new Object[_size];
int i = 0;
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
array[i++] = elt.value();
}
return array;
}
/**
* Returns an array containing all of the elements in this list in proper
* sequence; the runtime type of the returned array is that of the
* specified array. Obeys the general contract of the
* {@link Collection#toArray} method.
*
* @param a the array into which the elements of this 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 this list.
* @exception ArrayStoreException
* if the runtime type of the specified array
* is not a supertype of the runtime type of every element in
* this list.
*/
public Object[] toArray(Object a[]) {
if(a.length < _size) {
a = (Object[])Array.newInstance(a.getClass().getComponentType(), _size);
}
int i = 0;
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
a[i++] = elt.value();
}
if(a.length > _size) {
a[_size] = null; // should we null out the rest of the array also? java.util.LinkedList doesn't
}
return a;
}
/**
* Returns a {@link String} representation of this list, suitable for debugging.
* @return a {@link String} representation of this list, suitable for debugging.
*/
public String toString() {
StringBuffer buf = new StringBuffer();
buf.append("[");
for(Listable elt = _head.next(), past = null; null != elt && past != _head.prev(); elt = (past = elt).next()) {
if(_head.next() != elt) {
buf.append(", ");
}
buf.append(elt.value());
}
buf.append("]");
return buf.toString();
}
/**
* Returns a fail-fast sublist.
* @see List#subList(int,int)
*/
public List subList(int i, int j) {
if(i < 0 || j > _size || i > j) {
throw new IndexOutOfBoundsException();
} else if(i == 0 && j == _size) {
return this;
} else {
return new CursorableSubList(this,i,j);
}
}
//--- protected methods ------------------------------------------
/**
* Inserts a new <i>value into my
* list, after the specified <i>before element, and before the
* specified <i>after element
*
* @return the newly created
* {@link org.apache.commons.collections.CursorableLinkedList.Listable}
*/
protected Listable insertListable(Listable before, Listable after, Object value) {
_modCount++;
_size++;
Listable elt = new Listable(before,after,value);
if(null != before) {
before.setNext(elt);
} else {
_head.setNext(elt);
}
if(null != after) {
after.setPrev(elt);
} else {
_head.setPrev(elt);
}
broadcastListableInserted(elt);
return elt;
}
/**
* Removes the given
* {@link org.apache.commons.collections.CursorableLinkedList.Listable}
* from my list.
*/
protected void removeListable(Listable elt) {
_modCount++;
_size--;
if(_head.next() == elt) {
_head.setNext(elt.next());
}
if(null != elt.next()) {
elt.next().setPrev(elt.prev());
}
if(_head.prev() == elt) {
_head.setPrev(elt.prev());
}
if(null != elt.prev()) {
elt.prev().setNext(elt.next());
}
broadcastListableRemoved(elt);
}
/**
* Returns the
* {@link org.apache.commons.collections.CursorableLinkedList.Listable}
* at the specified index.
*
* @throws IndexOutOfBoundsException if index is less than zero or
* greater than or equal to the size of this list.
*/
protected Listable getListableAt(int index) {
if(index < 0 || index >= _size) {
throw new IndexOutOfBoundsException(String.valueOf(index) + " < 0 or " + String.valueOf(index) + " >= " + _size);
}
if(index <=_size/2) {
Listable elt = _head.next();
for(int i = 0; i < index; i++) {
elt = elt.next();
}
return elt;
} else {
Listable elt = _head.prev();
for(int i = (_size-1); i > index; i--) {
elt = elt.prev();
}
return elt;
}
}
/**
* Registers a {@link CursorableLinkedList.Cursor} to be notified
* of changes to this list.
*/
protected void registerCursor(Cursor cur) {
// We take this opportunity to clean the _cursors list
// of WeakReference objects to garbage-collected cursors.
for (Iterator it = _cursors.iterator(); it.hasNext(); ) {
WeakReference ref = (WeakReference) it.next();
if (ref.get() == null) {
it.remove();
}
}
_cursors.add( new WeakReference(cur) );
}
/**
* Removes a {@link CursorableLinkedList.Cursor} from
* the set of cursors to be notified of changes to this list.
*/
protected void unregisterCursor(Cursor cur) {
for (Iterator it = _cursors.iterator(); it.hasNext(); ) {
WeakReference ref = (WeakReference) it.next();
Cursor cursor = (Cursor) ref.get();
if (cursor == null) {
// some other unrelated cursor object has been
// garbage-collected; let's take the opportunity to
// clean up the cursors list anyway..
it.remove();
} else if (cursor == cur) {
ref.clear();
it.remove();
break;
}
}
}
/**
* Informs all of my registered cursors that they are now
* invalid.
*/
protected void invalidateCursors() {
Iterator it = _cursors.iterator();
while (it.hasNext()) {
WeakReference ref = (WeakReference) it.next();
Cursor cursor = (Cursor) ref.get();
if (cursor != null) {
// cursor is null if object has been garbage-collected
cursor.invalidate();
ref.clear();
}
it.remove();
}
}
/**
* Informs all of my registered cursors that the specified
* element was changed.
* @see #set(int,java.lang.Object)
*/
protected void broadcastListableChanged(Listable elt) {
Iterator it = _cursors.iterator();
while (it.hasNext()) {
WeakReference ref = (WeakReference) it.next();
Cursor cursor = (Cursor) ref.get();
if (cursor == null) {
it.remove(); // clean up list
} else {
cursor.listableChanged(elt);
}
}
}
/**
* Informs all of my registered cursors that the specified
* element was just removed from my list.
*/
protected void broadcastListableRemoved(Listable elt) {
Iterator it = _cursors.iterator();
while (it.hasNext()) {
WeakReference ref = (WeakReference) it.next();
Cursor cursor = (Cursor) ref.get();
if (cursor == null) {
it.remove(); // clean up list
} else {
cursor.listableRemoved(elt);
}
}
}
/**
* Informs all of my registered cursors that the specified
* element was just added to my list.
*/
protected void broadcastListableInserted(Listable elt) {
Iterator it = _cursors.iterator();
while (it.hasNext()) {
WeakReference ref = (WeakReference) it.next();
Cursor cursor = (Cursor) ref.get();
if (cursor == null) {
it.remove(); // clean up list
} else {
cursor.listableInserted(elt);
}
}
}
private void writeObject(ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeInt(_size);
Listable cur = _head.next();
while (cur != null) {
out.writeObject(cur.value());
cur = cur.next();
}
}
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
_size = 0;
_modCount = 0;
_cursors = new ArrayList();
_head = new Listable(null,null,null);
int size = in.readInt();
for (int i=0;i<size;i++) {
this.add(in.readObject());
}
}
//--- protected attributes ---------------------------------------
/** The number of elements in me. */
protected transient int _size = 0;
/**
* A sentry node.
* <p>
* <tt>_head.next() points to the first element in the list,
* <tt>_head.prev() to the last. Note that it is possible for
* <tt>_head.next().prev() and _head.prev().next() to be
* non-null, as when I am a sublist for some larger list.
* Use <tt>== _head.next() and == _head.prev() to determine
* if a given
* {@link org.apache.commons.collections.CursorableLinkedList.Listable}
* is the first or last element in the list.
*/
protected transient Listable _head = new Listable(null,null,null);
/** Tracks the number of structural modifications to me. */
protected transient int _modCount = 0;
/**
* A list of the currently {@link CursorableLinkedList.Cursor}s currently
* open in this list.
*/
protected transient List _cursors = new ArrayList();
//--- inner classes ----------------------------------------------
static class Listable implements Serializable {
private Listable _prev = null;
private Listable _next = null;
private Object _val = null;
Listable(Listable prev, Listable next, Object val) {
_prev = prev;
_next = next;
_val = val;
}
Listable next() {
return _next;
}
Listable prev() {
return _prev;
}
Object value() {
return _val;
}
void setNext(Listable next) {
_next = next;
}
void setPrev(Listable prev) {
_prev = prev;
}
Object setValue(Object val) {
Object temp = _val;
_val = val;
return temp;
}
}
class ListIter implements ListIterator {
Listable _cur = null;
Listable _lastReturned = null;
int _expectedModCount = _modCount;
int _nextIndex = 0;
ListIter(int index) {
if(index == 0) {
_cur = new Listable(null,_head.next(),null);
_nextIndex = 0;
} else if(index == _size) {
_cur = new Listable(_head.prev(),null,null);
_nextIndex = _size;
} else {
Listable temp = getListableAt(index);
_cur = new Listable(temp.prev(),temp,null);
_nextIndex = index;
}
}
public Object previous() {
checkForComod();
if(!hasPrevious()) {
throw new NoSuchElementException();
} else {
Object ret = _cur.prev().value();
_lastReturned = _cur.prev();
_cur.setNext(_cur.prev());
_cur.setPrev(_cur.prev().prev());
_nextIndex--;
return ret;
}
}
public boolean hasNext() {
checkForComod();
return(null != _cur.next() && _cur.prev() != _head.prev());
}
public Object next() {
checkForComod();
if(!hasNext()) {
throw new NoSuchElementException();
} else {
Object ret = _cur.next().value();
_lastReturned = _cur.next();
_cur.setPrev(_cur.next());
_cur.setNext(_cur.next().next());
_nextIndex++;
return ret;
}
}
public int previousIndex() {
checkForComod();
if(!hasPrevious()) {
return -1;
}
return _nextIndex-1;
}
public boolean hasPrevious() {
checkForComod();
return(null != _cur.prev() && _cur.next() != _head.next());
}
public void set(Object o) {
checkForComod();
try {
_lastReturned.setValue(o);
} catch(NullPointerException e) {
throw new IllegalStateException();
}
}
public int nextIndex() {
checkForComod();
if(!hasNext()) {
return size();
}
return _nextIndex;
}
public void remove() {
checkForComod();
if(null == _lastReturned) {
throw new IllegalStateException();
} else {
_cur.setNext(_lastReturned == _head.prev() ? null : _lastReturned.next());
_cur.setPrev(_lastReturned == _head.next() ? null : _lastReturned.prev());
removeListable(_lastReturned);
_lastReturned = null;
_nextIndex--;
_expectedModCount++;
}
}
public void add(Object o) {
checkForComod();
_cur.setPrev(insertListable(_cur.prev(),_cur.next(),o));
_lastReturned = null;
_nextIndex++;
_expectedModCount++;
}
protected void checkForComod() {
if(_expectedModCount != _modCount) {
throw new ConcurrentModificationException();
}
}
}
public class Cursor extends ListIter implements ListIterator {
boolean _valid = false;
Cursor(int index) {
super(index);
_valid = true;
registerCursor(this);
}
public int previousIndex() {
throw new UnsupportedOperationException();
}
public int nextIndex() {
throw new UnsupportedOperationException();
}
public void add(Object o) {
checkForComod();
Listable elt = insertListable(_cur.prev(),_cur.next(),o);
_cur.setPrev(elt);
_cur.setNext(elt.next());
_lastReturned = null;
_nextIndex++;
_expectedModCount++;
}
protected void listableRemoved(Listable elt) {
if(null == _head.prev()) {
_cur.setNext(null);
} else if(_cur.next() == elt) {
_cur.setNext(elt.next());
}
if(null == _head.next()) {
_cur.setPrev(null);
} else if(_cur.prev() == elt) {
_cur.setPrev(elt.prev());
}
if(_lastReturned == elt) {
_lastReturned = null;
}
}
protected void listableInserted(Listable elt) {
if(null == _cur.next() && null == _cur.prev()) {
_cur.setNext(elt);
} else if(_cur.prev() == elt.prev()) {
_cur.setNext(elt);
}
if(_cur.next() == elt.next()) {
_cur.setPrev(elt);
}
if(_lastReturned == elt) {
_lastReturned = null;
}
}
protected void listableChanged(Listable elt) {
if(_lastReturned == elt) {
_lastReturned = null;
}
}
protected void checkForComod() {
if(!_valid) {
throw new ConcurrentModificationException();
}
}
protected void invalidate() {
_valid = false;
}
/**
* Mark this cursor as no longer being needed. Any resources
* associated with this cursor are immediately released.
* In previous versions of this class, it was mandatory to close
* all cursor objects to avoid memory leaks. It is <i>no longer
* necessary to call this close method; an instance of this class
* can now be treated exactly like a normal iterator.
*/
public void close() {
if(_valid) {
_valid = false;
unregisterCursor(this);
}
}
}
}
/**
* @deprecated Use new version in list subpackage, which has been rewritten
* and now returns the cursor from the listIterator method. Will be removed in v4.0
*/
class CursorableSubList extends CursorableLinkedList implements List {
//--- constructors -----------------------------------------------
CursorableSubList(CursorableLinkedList list, int from, int to) {
if(0 > from || list.size() < to) {
throw new IndexOutOfBoundsException();
} else if(from > to) {
throw new IllegalArgumentException();
}
_list = list;
if(from < list.size()) {
_head.setNext(_list.getListableAt(from));
_pre = (null == _head.next()) ? null : _head.next().prev();
} else {
_pre = _list.getListableAt(from-1);
}
if(from == to) {
_head.setNext(null);
_head.setPrev(null);
if(to < list.size()) {
_post = _list.getListableAt(to);
} else {
_post = null;
}
} else {
_head.setPrev(_list.getListableAt(to-1));
_post = _head.prev().next();
}
_size = to - from;
_modCount = _list._modCount;
}
//--- public methods ------------------------------------------
public void clear() {
checkForComod();
Iterator it = iterator();
while(it.hasNext()) {
it.next();
it.remove();
}
}
public Iterator iterator() {
checkForComod();
return super.iterator();
}
public int size() {
checkForComod();
return super.size();
}
public boolean isEmpty() {
checkForComod();
return super.isEmpty();
}
public Object[] toArray() {
checkForComod();
return super.toArray();
}
public Object[] toArray(Object a[]) {
checkForComod();
return super.toArray(a);
}
public boolean contains(Object o) {
checkForComod();
return super.contains(o);
}
public boolean remove(Object o) {
checkForComod();
return super.remove(o);
}
public Object removeFirst() {
checkForComod();
return super.removeFirst();
}
public Object removeLast() {
checkForComod();
return super.removeLast();
}
public boolean addAll(Collection c) {
checkForComod();
return super.addAll(c);
}
public boolean add(Object o) {
checkForComod();
return super.add(o);
}
public boolean addFirst(Object o) {
checkForComod();
return super.addFirst(o);
}
public boolean addLast(Object o) {
checkForComod();
return super.addLast(o);
}
public boolean removeAll(Collection c) {
checkForComod();
return super.removeAll(c);
}
public boolean containsAll(Collection c) {
checkForComod();
return super.containsAll(c);
}
public boolean addAll(int index, Collection c) {
checkForComod();
return super.addAll(index,c);
}
public int hashCode() {
checkForComod();
return super.hashCode();
}
public boolean retainAll(Collection c) {
checkForComod();
return super.retainAll(c);
}
public Object set(int index, Object element) {
checkForComod();
return super.set(index,element);
}
public boolean equals(Object o) {
checkForComod();
return super.equals(o);
}
public Object get(int index) {
checkForComod();
return super.get(index);
}
public Object getFirst() {
checkForComod();
return super.getFirst();
}
public Object getLast() {
checkForComod();
return super.getLast();
}
public void add(int index, Object element) {
checkForComod();
super.add(index,element);
}
public ListIterator listIterator(int index) {
checkForComod();
return super.listIterator(index);
}
public Object remove(int index) {
checkForComod();
return super.remove(index);
}
public int indexOf(Object o) {
checkForComod();
return super.indexOf(o);
}
public int lastIndexOf(Object o) {
checkForComod();
return super.lastIndexOf(o);
}
public ListIterator listIterator() {
checkForComod();
return super.listIterator();
}
public List subList(int fromIndex, int toIndex) {
checkForComod();
return super.subList(fromIndex,toIndex);
}
//--- protected methods ------------------------------------------
/**
* Inserts a new <i>value into my
* list, after the specified <i>before element, and before the
* specified <i>after element
*
* @return the newly created {@link CursorableLinkedList.Listable}
*/
protected Listable insertListable(Listable before, Listable after, Object value) {
_modCount++;
_size++;
Listable elt = _list.insertListable((null == before ? _pre : before), (null == after ? _post : after),value);
if(null == _head.next()) {
_head.setNext(elt);
_head.setPrev(elt);
}
if(before == _head.prev()) {
_head.setPrev(elt);
}
if(after == _head.next()) {
_head.setNext(elt);
}
broadcastListableInserted(elt);
return elt;
}
/**
* Removes the given {@link CursorableLinkedList.Listable} from my list.
*/
protected void removeListable(Listable elt) {
_modCount++;
_size--;
if(_head.next() == elt && _head.prev() == elt) {
_head.setNext(null);
_head.setPrev(null);
}
if(_head.next() == elt) {
_head.setNext(elt.next());
}
if(_head.prev() == elt) {
_head.setPrev(elt.prev());
}
_list.removeListable(elt);
broadcastListableRemoved(elt);
}
/**
* Test to see if my underlying list has been modified
* by some other process. If it has, throws a
* {@link ConcurrentModificationException}, otherwise
* quietly returns.
*
* @throws ConcurrentModificationException
*/
protected void checkForComod() throws ConcurrentModificationException {
if(_modCount != _list._modCount) {
throw new ConcurrentModificationException();
}
}
//--- protected attributes ---------------------------------------
/** My underlying list */
protected CursorableLinkedList _list = null;
/** The element in my underlying list preceding the first element in my list. */
protected Listable _pre = null;
/** The element in my underlying list following the last element in my list. */
protected Listable _post = null;
}
Other Commons Collections examples (source code examples)Here is a short list of links related to this Commons Collections CursorableLinkedList.java source code file: |
The search page
Other Commons Collections source code examples at this package level
Click here to learn more about this project
