Mega Code Archive
Customized java util ArrayList
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/*
* 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.
*/
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
/**
* <p>A customized implementation of <code>java.util.ArrayList</code> designed
* to operate in a multithreaded environment where the large majority of
* method calls are read-only, instead of structural changes. When operating
* in "fast" mode, read calls are non-synchronized and write calls perform the
* following steps:</p>
* <ul>
* <li>Clone the existing collection
* <li>Perform the modification on the clone
* <li>Replace the existing collection with the (modified) clone
* </ul>
* <p>When first created, objects of this class default to "slow" mode, where
* all accesses of any type are synchronized but no cloning takes place. This
* is appropriate for initially populating the collection, followed by a switch
* to "fast" mode (by calling <code>setFast(true)</code>) after initialization
* is complete.</p>
*
* <p><strong>NOTE</strong>: If you are creating and accessing an
* <code>ArrayList</code> only within a single thread, you should use
* <code>java.util.ArrayList</code> directly (with no synchronization), for
* maximum performance.</p>
*
* <p><strong>NOTE</strong>: <i>This class is not cross-platform.
* Using it may cause unexpected failures on some architectures.</i>
* It suffers from the same problems as the double-checked locking idiom.
* In particular, the instruction that clones the internal collection and the
* instruction that sets the internal reference to the clone can be executed
* or perceived out-of-order. This means that any read operation might fail
* unexpectedly, as it may be reading the state of the internal collection
* before the internal collection is fully formed.
* For more information on the double-checked locking idiom, see the
* <a href="http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html">
* Double-Checked Locking Idiom Is Broken Declaration</a>.</p>
*
* @since Commons Collections 1.0
* @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
*
* @author Craig R. McClanahan
* @author Stephen Colebourne
*/
public class FastArrayList extends ArrayList {
// ----------------------------------------------------------- Constructors
/**
* Construct a an empty list.
*/
public FastArrayList() {
super();
this.list = new ArrayList();
}
/**
* Construct an empty list with the specified capacity.
*
* @param capacity The initial capacity of the empty list
*/
public FastArrayList(int capacity) {
super();
this.list = new ArrayList(capacity);
}
/**
* Construct a list containing the elements of the specified collection,
* in the order they are returned by the collection's iterator.
*
* @param collection The collection whose elements initialize the contents
* of this list
*/
public FastArrayList(Collection collection) {
super();
this.list = new ArrayList(collection);
}
// ----------------------------------------------------- Instance Variables
/**
* The underlying list we are managing.
*/
protected ArrayList list = null;
// ------------------------------------------------------------- Properties
/**
* Are we operating in "fast" mode?
*/
protected boolean fast = false;
/**
* Returns true if this list is operating in fast mode.
*
* @return true if this list is operating in fast mode
*/
public boolean getFast() {
return (this.fast);
}
/**
* Sets whether this list will operate in fast mode.
*
* @param fast true if the list should operate in fast mode
*/
public void setFast(boolean fast) {
this.fast = fast;
}
// --------------------------------------------------------- Public Methods
/**
* Appends the specified element to the end of this list.
*
* @param element The element to be appended
*/
public boolean add(Object element) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
boolean result = temp.add(element);
list = temp;
return (result);
}
} else {
synchronized (list) {
return (list.add(element));
}
}
}
/**
* Insert the specified element at the specified position in this list,
* and shift all remaining elements up one position.
*
* @param index Index at which to insert this element
* @param element The element to be inserted
*
* @exception IndexOutOfBoundsException if the index is out of range
*/
public void add(int index, Object element) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
temp.add(index, element);
list = temp;
}
} else {
synchronized (list) {
list.add(index, element);
}
}
}
/**
* Append 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.
*
* @param collection The collection to be appended
*/
public boolean addAll(Collection collection) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
boolean result = temp.addAll(collection);
list = temp;
return (result);
}
} else {
synchronized (list) {
return (list.addAll(collection));
}
}
}
/**
* Insert all of the elements in the specified Collection at the specified
* position in this list, and shift any previous elements upwards as
* needed.
*
* @param index Index at which insertion takes place
* @param collection The collection to be added
*
* @exception IndexOutOfBoundsException if the index is out of range
*/
public boolean addAll(int index, Collection collection) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
boolean result = temp.addAll(index, collection);
list = temp;
return (result);
}
} else {
synchronized (list) {
return (list.addAll(index, collection));
}
}
}
/**
* Remove all of the elements from this list. The list will be empty
* after this call returns.
*
* @exception UnsupportedOperationException if <code>clear()</code>
* is not supported by this list
*/
public void clear() {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
temp.clear();
list = temp;
}
} else {
synchronized (list) {
list.clear();
}
}
}
/**
* Return a shallow copy of this <code>FastArrayList</code> instance.
* The elements themselves are not copied.
*/
public Object clone() {
FastArrayList results = null;
if (fast) {
results = new FastArrayList(list);
} else {
synchronized (list) {
results = new FastArrayList(list);
}
}
results.setFast(getFast());
return (results);
}
/**
* Return <code>true</code> if this list contains the specified element.
*
* @param element The element to test for
*/
public boolean contains(Object element) {
if (fast) {
return (list.contains(element));
} else {
synchronized (list) {
return (list.contains(element));
}
}
}
/**
* Return <code>true</code> if this list contains all of the elements
* in the specified Collection.
*
* @param collection Collection whose elements are to be checked
*/
public boolean containsAll(Collection collection) {
if (fast) {
return (list.containsAll(collection));
} else {
synchronized (list) {
return (list.containsAll(collection));
}
}
}
/**
* Increase the capacity of this <code>ArrayList</code> instance, if
* necessary, to ensure that it can hold at least the number of elements
* specified by the minimum capacity argument.
*
* @param capacity The new minimum capacity
*/
public void ensureCapacity(int capacity) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
temp.ensureCapacity(capacity);
list = temp;
}
} else {
synchronized (list) {
list.ensureCapacity(capacity);
}
}
}
/**
* Compare the specified object with this list for equality. This
* implementation uses exactly the code that is used to define the
* list equals function in the documentation for the
* <code>List.equals</code> method.
*
* @param o Object to be compared to this list
*/
public boolean equals(Object o) {
// Simple tests that require no synchronization
if (o == this)
return (true);
else if (!(o instanceof List))
return (false);
List lo = (List) o;
// Compare the sets of elements for equality
if (fast) {
ListIterator li1 = list.listIterator();
ListIterator li2 = lo.listIterator();
while (li1.hasNext() && li2.hasNext()) {
Object o1 = li1.next();
Object o2 = li2.next();
if (!(o1 == null ? o2 == null : o1.equals(o2)))
return (false);
}
return (!(li1.hasNext() || li2.hasNext()));
} else {
synchronized (list) {
ListIterator li1 = list.listIterator();
ListIterator li2 = lo.listIterator();
while (li1.hasNext() && li2.hasNext()) {
Object o1 = li1.next();
Object o2 = li2.next();
if (!(o1 == null ? o2 == null : o1.equals(o2)))
return (false);
}
return (!(li1.hasNext() || li2.hasNext()));
}
}
}
/**
* Return the element at the specified position in the list.
*
* @param index The index of the element to return
*
* @exception IndexOutOfBoundsException if the index is out of range
*/
public Object get(int index) {
if (fast) {
return (list.get(index));
} else {
synchronized (list) {
return (list.get(index));
}
}
}
/**
* Return the hash code value for this list. This implementation uses
* exactly the code that is used to define the list hash function in the
* documentation for the <code>List.hashCode</code> method.
*/
public int hashCode() {
if (fast) {
int hashCode = 1;
java.util.Iterator i = list.iterator();
while (i.hasNext()) {
Object o = i.next();
hashCode = 31 * hashCode + (o == null ? 0 : o.hashCode());
}
return (hashCode);
} else {
synchronized (list) {
int hashCode = 1;
java.util.Iterator i = list.iterator();
while (i.hasNext()) {
Object o = i.next();
hashCode = 31 * hashCode + (o == null ? 0 : o.hashCode());
}
return (hashCode);
}
}
}
/**
* Search for the first occurrence of the given argument, testing
* for equality using the <code>equals()</code> method, and return
* the corresponding index, or -1 if the object is not found.
*
* @param element The element to search for
*/
public int indexOf(Object element) {
if (fast) {
return (list.indexOf(element));
} else {
synchronized (list) {
return (list.indexOf(element));
}
}
}
/**
* Test if this list has no elements.
*/
public boolean isEmpty() {
if (fast) {
return (list.isEmpty());
} else {
synchronized (list) {
return (list.isEmpty());
}
}
}
/**
* Return an iterator over the elements in this list in proper sequence.
* <p>
* <b>Thread safety</b><br />
* The iterator returned is thread-safe ONLY in FAST mode.
* In slow mode there is no way to synchronize, or make the iterator thread-safe.
* <p>
* In fast mode iteration and modification may occur in parallel on different threads,
* however there is a restriction. Modification must be EITHER via the Iterator
* interface methods OR the List interface. If a mixture of modification
* methods is used a ConcurrentModificationException is thrown from the iterator
* modification method. If the List modification methods are used the changes are
* NOT visible in the iterator (it shows the list contents at the time the iterator
* was created).
*
* @return the iterator
*/
public Iterator iterator() {
if (fast) {
return new ListIter(0);
} else {
return list.iterator();
}
}
/**
* Search for the last occurrence of the given argument, testing
* for equality using the <code>equals()</code> method, and return
* the corresponding index, or -1 if the object is not found.
*
* @param element The element to search for
*/
public int lastIndexOf(Object element) {
if (fast) {
return (list.lastIndexOf(element));
} else {
synchronized (list) {
return (list.lastIndexOf(element));
}
}
}
/**
* Return an iterator of the elements of this list, in proper sequence.
* <p>
* <b>Thread safety</b><br />
* The iterator returned is thread-safe ONLY in FAST mode.
* In slow mode there is no way to synchronize, or make the iterator thread-safe.
* <p>
* In fast mode iteration and modification may occur in parallel on different threads,
* however there is a restriction. Modification must be EITHER via the Iterator
* interface methods OR the List interface. If a mixture of modification
* methods is used a ConcurrentModificationException is thrown from the iterator
* modification method. If the List modification methods are used the changes are
* NOT visible in the iterator (it shows the list contents at the time the iterator
* was created).
*
* @return the list iterator
*/
public ListIterator listIterator() {
if (fast) {
return new ListIter(0);
} else {
return list.listIterator();
}
}
/**
* Return an iterator of the elements of this list, in proper sequence,
* starting at the specified position.
* <p>
* <b>Thread safety</b><br />
* The iterator returned is thread-safe ONLY in FAST mode.
* In slow mode there is no way to synchronize, or make the iterator thread-safe.
* <p>
* In fast mode iteration and modification may occur in parallel on different threads,
* however there is a restriction. Modification must be EITHER via the Iterator
* interface methods OR the List interface. If a mixture of modification
* methods is used a ConcurrentModificationException is thrown from the iterator
* modification method. If the List modification methods are used the changes are
* NOT visible in the iterator (it shows the list contents at the time the iterator
* was created).
*
* @param index The starting position of the iterator to return
* @return the list iterator
* @exception IndexOutOfBoundsException if the index is out of range
*/
public ListIterator listIterator(int index) {
if (fast) {
return new ListIter(index);
} else {
return list.listIterator(index);
}
}
/**
* Remove the element at the specified position in the list, and shift
* any subsequent elements down one position.
*
* @param index Index of the element to be removed
*
* @exception IndexOutOfBoundsException if the index is out of range
*/
public Object remove(int index) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
Object result = temp.remove(index);
list = temp;
return (result);
}
} else {
synchronized (list) {
return (list.remove(index));
}
}
}
/**
* Remove the first occurrence of the specified element from the list,
* and shift any subsequent elements down one position.
*
* @param element Element to be removed
*/
public boolean remove(Object element) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
boolean result = temp.remove(element);
list = temp;
return (result);
}
} else {
synchronized (list) {
return (list.remove(element));
}
}
}
/**
* Remove from this collection all of its elements that are contained
* in the specified collection.
*
* @param collection Collection containing elements to be removed
*
* @exception UnsupportedOperationException if this optional operation
* is not supported by this list
*/
public boolean removeAll(Collection collection) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
boolean result = temp.removeAll(collection);
list = temp;
return (result);
}
} else {
synchronized (list) {
return (list.removeAll(collection));
}
}
}
/**
* Remove from this collection all of its elements except those that are
* contained in the specified collection.
*
* @param collection Collection containing elements to be retained
*
* @exception UnsupportedOperationException if this optional operation
* is not supported by this list
*/
public boolean retainAll(Collection collection) {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
boolean result = temp.retainAll(collection);
list = temp;
return (result);
}
} else {
synchronized (list) {
return (list.retainAll(collection));
}
}
}
/**
* Replace the element at the specified position in this list with
* the specified element. Returns the previous object at that position.
* <br><br>
* <strong>IMPLEMENTATION NOTE</strong> - This operation is specifically
* documented to not be a structural change, so it is safe to be performed
* without cloning.
*
* @param index Index of the element to replace
* @param element The new element to be stored
*
* @exception IndexOutOfBoundsException if the index is out of range
*/
public Object set(int index, Object element) {
if (fast) {
return (list.set(index, element));
} else {
synchronized (list) {
return (list.set(index, element));
}
}
}
/**
* Return the number of elements in this list.
*/
public int size() {
if (fast) {
return (list.size());
} else {
synchronized (list) {
return (list.size());
}
}
}
/**
* Return a view of the portion of this list between fromIndex
* (inclusive) and toIndex (exclusive). The returned list is backed
* by this list, so non-structural changes in the returned list are
* reflected in this list. The returned list supports
* all of the optional list operations supported by this list.
*
* @param fromIndex The starting index of the sublist view
* @param toIndex The index after the end of the sublist view
*
* @exception IndexOutOfBoundsException if an index is out of range
*/
public List subList(int fromIndex, int toIndex) {
if (fast) {
return new SubList(fromIndex, toIndex);
} else {
return list.subList(fromIndex, toIndex);
}
}
/**
* Return an array containing all of the elements in this list in the
* correct order.
*/
public Object[] toArray() {
if (fast) {
return (list.toArray());
} else {
synchronized (list) {
return (list.toArray());
}
}
}
/**
* Return an array containing all of the elements in this list in the
* correct order. The runtime type of the returned array is that of
* the specified array. If the list fits in the specified array, it is
* returned therein. Otherwise, a new array is allocated with the
* runtime type of the specified array, and the size of this list.
*
* @param array Array defining the element type of the returned list
*
* @exception ArrayStoreException if the runtime type of <code>array</code>
* is not a supertype of the runtime type of every element in this list
*/
public Object[] toArray(Object array[]) {
if (fast) {
return (list.toArray(array));
} else {
synchronized (list) {
return (list.toArray(array));
}
}
}
/**
* Return a String representation of this object.
*/
public String toString() {
StringBuffer sb = new StringBuffer("FastArrayList[");
sb.append(list.toString());
sb.append("]");
return (sb.toString());
}
/**
* Trim the capacity of this <code>ArrayList</code> instance to be the
* list's current size. An application can use this operation to minimize
* the storage of an <code>ArrayList</code> instance.
*/
public void trimToSize() {
if (fast) {
synchronized (this) {
ArrayList temp = (ArrayList) list.clone();
temp.trimToSize();
list = temp;
}
} else {
synchronized (list) {
list.trimToSize();
}
}
}
private class SubList implements List {
private int first;
private int last;
private List expected;
public SubList(int first, int last) {
this.first = first;
this.last = last;
this.expected = list;
}
private List get(List l) {
if (list != expected) {
throw new ConcurrentModificationException();
}
return l.subList(first, last);
}
public void clear() {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
get(temp).clear();
last = first;
list = temp;
expected = temp;
}
} else {
synchronized (list) {
get(expected).clear();
}
}
}
public boolean remove(Object o) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
boolean r = get(temp).remove(o);
if (r) last--;
list = temp;
expected = temp;
return r;
}
} else {
synchronized (list) {
return get(expected).remove(o);
}
}
}
public boolean removeAll(Collection o) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
List sub = get(temp);
boolean r = sub.removeAll(o);
if (r) last = first + sub.size();
list = temp;
expected = temp;
return r;
}
} else {
synchronized (list) {
return get(expected).removeAll(o);
}
}
}
public boolean retainAll(Collection o) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
List sub = get(temp);
boolean r = sub.retainAll(o);
if (r) last = first + sub.size();
list = temp;
expected = temp;
return r;
}
} else {
synchronized (list) {
return get(expected).retainAll(o);
}
}
}
public int size() {
if (fast) {
return get(expected).size();
} else {
synchronized (list) {
return get(expected).size();
}
}
}
public boolean isEmpty() {
if (fast) {
return get(expected).isEmpty();
} else {
synchronized (list) {
return get(expected).isEmpty();
}
}
}
public boolean contains(Object o) {
if (fast) {
return get(expected).contains(o);
} else {
synchronized (list) {
return get(expected).contains(o);
}
}
}
public boolean containsAll(Collection o) {
if (fast) {
return get(expected).containsAll(o);
} else {
synchronized (list) {
return get(expected).containsAll(o);
}
}
}
public Object[] toArray(Object[] o) {
if (fast) {
return get(expected).toArray(o);
} else {
synchronized (list) {
return get(expected).toArray(o);
}
}
}
public Object[] toArray() {
if (fast) {
return get(expected).toArray();
} else {
synchronized (list) {
return get(expected).toArray();
}
}
}
public boolean equals(Object o) {
if (o == this) return true;
if (fast) {
return get(expected).equals(o);
} else {
synchronized (list) {
return get(expected).equals(o);
}
}
}
public int hashCode() {
if (fast) {
return get(expected).hashCode();
} else {
synchronized (list) {
return get(expected).hashCode();
}
}
}
public boolean add(Object o) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
boolean r = get(temp).add(o);
if (r) last++;
list = temp;
expected = temp;
return r;
}
} else {
synchronized (list) {
return get(expected).add(o);
}
}
}
public boolean addAll(Collection o) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
boolean r = get(temp).addAll(o);
if (r) last += o.size();
list = temp;
expected = temp;
return r;
}
} else {
synchronized (list) {
return get(expected).addAll(o);
}
}
}
public void add(int i, Object o) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
get(temp).add(i, o);
last++;
list = temp;
expected = temp;
}
} else {
synchronized (list) {
get(expected).add(i, o);
}
}
}
public boolean addAll(int i, Collection o) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
boolean r = get(temp).addAll(i, o);
list = temp;
if (r) last += o.size();
expected = temp;
return r;
}
} else {
synchronized (list) {
return get(expected).addAll(i, o);
}
}
}
public Object remove(int i) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
Object o = get(temp).remove(i);
last--;
list = temp;
expected = temp;
return o;
}
} else {
synchronized (list) {
return get(expected).remove(i);
}
}
}
public Object set(int i, Object a) {
if (fast) {
synchronized (FastArrayList.this) {
ArrayList temp = (ArrayList) list.clone();
Object o = get(temp).set(i, a);
list = temp;
expected = temp;
return o;
}
} else {
synchronized (list) {
return get(expected).set(i, a);
}
}
}
public Iterator iterator() {
return new SubListIter(0);
}
public ListIterator listIterator() {
return new SubListIter(0);
}
public ListIterator listIterator(int i) {
return new SubListIter(i);
}
public Object get(int i) {
if (fast) {
return get(expected).get(i);
} else {
synchronized (list) {
return get(expected).get(i);
}
}
}
public int indexOf(Object o) {
if (fast) {
return get(expected).indexOf(o);
} else {
synchronized (list) {
return get(expected).indexOf(o);
}
}
}
public int lastIndexOf(Object o) {
if (fast) {
return get(expected).lastIndexOf(o);
} else {
synchronized (list) {
return get(expected).lastIndexOf(o);
}
}
}
public List subList(int f, int l) {
if (list != expected) {
throw new ConcurrentModificationException();
}
return new SubList(first + f, f + l);
}
private class SubListIter implements ListIterator {
private List expected;
private ListIterator iter;
private int lastReturnedIndex = -1;
public SubListIter(int i) {
this.expected = list;
this.iter = SubList.this.get(expected).listIterator(i);
}
private void checkMod() {
if (list != expected) {
throw new ConcurrentModificationException();
}
}
List get() {
return SubList.this.get(expected);
}
public boolean hasNext() {
checkMod();
return iter.hasNext();
}
public Object next() {
checkMod();
lastReturnedIndex = iter.nextIndex();
return iter.next();
}
public boolean hasPrevious() {
checkMod();
return iter.hasPrevious();
}
public Object previous() {
checkMod();
lastReturnedIndex = iter.previousIndex();
return iter.previous();
}
public int previousIndex() {
checkMod();
return iter.previousIndex();
}
public int nextIndex() {
checkMod();
return iter.nextIndex();
}
public void remove() {
checkMod();
if (lastReturnedIndex < 0) {
throw new IllegalStateException();
}
get().remove(lastReturnedIndex);
last--;
expected = list;
iter = get().listIterator(lastReturnedIndex);
lastReturnedIndex = -1;
}
public void set(Object o) {
checkMod();
if (lastReturnedIndex < 0) {
throw new IllegalStateException();
}
get().set(lastReturnedIndex, o);
expected = list;
iter = get().listIterator(previousIndex() + 1);
}
public void add(Object o) {
checkMod();
int i = nextIndex();
get().add(i, o);
last++;
expected = list;
iter = get().listIterator(i + 1);
lastReturnedIndex = -1;
}
}
}
private class ListIter implements ListIterator {
private List expected;
private ListIterator iter;
private int lastReturnedIndex = -1;
public ListIter(int i) {
this.expected = list;
this.iter = get().listIterator(i);
}
private void checkMod() {
if (list != expected) {
throw new ConcurrentModificationException();
}
}
List get() {
return expected;
}
public boolean hasNext() {
return iter.hasNext();
}
public Object next() {
lastReturnedIndex = iter.nextIndex();
return iter.next();
}
public boolean hasPrevious() {
return iter.hasPrevious();
}
public Object previous() {
lastReturnedIndex = iter.previousIndex();
return iter.previous();
}
public int previousIndex() {
return iter.previousIndex();
}
public int nextIndex() {
return iter.nextIndex();
}
public void remove() {
checkMod();
if (lastReturnedIndex < 0) {
throw new IllegalStateException();
}
get().remove(lastReturnedIndex);
expected = list;
iter = get().listIterator(lastReturnedIndex);
lastReturnedIndex = -1;
}
public void set(Object o) {
checkMod();
if (lastReturnedIndex < 0) {
throw new IllegalStateException();
}
get().set(lastReturnedIndex, o);
expected = list;
iter = get().listIterator(previousIndex() + 1);
}
public void add(Object o) {
checkMod();
int i = nextIndex();
get().add(i, o);
expected = list;
iter = get().listIterator(i + 1);
lastReturnedIndex = -1;
}
}
}
]]>