java.util.AbstractList Maven / Gradle / Ivy
/*
* 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 java.util;
/**
* {@code AbstractList} is an abstract implementation of the {@code List} interface, optimized
* for a backing store which supports random access. This implementation does
* not support adding or replacing. A subclass must implement the abstract
* methods {@code get()} and {@code size()}, and to create a
* modifiable {@code List} it's necessary to override the {@code add()} method that
* currently throws an {@code UnsupportedOperationException}.
*
* @since 1.2
*/
public abstract class AbstractList extends AbstractCollection implements List {
/**
* A counter for changes to the list.
*/
protected transient int modCount;
private class SimpleListIterator implements Iterator {
int pos = -1;
int expectedModCount;
int lastPosition = -1;
SimpleListIterator() {
expectedModCount = modCount;
}
public boolean hasNext() {
return pos + 1 < size();
}
public E next() {
if (expectedModCount == modCount) {
try {
E result = get(pos + 1);
lastPosition = ++pos;
return result;
} catch (IndexOutOfBoundsException e) {
throw new NoSuchElementException();
}
}
throw new ConcurrentModificationException();
}
public void remove() {
if (this.lastPosition == -1) {
throw new IllegalStateException();
}
if (expectedModCount != modCount) {
throw new ConcurrentModificationException();
}
try {
AbstractList.this.remove(lastPosition);
} catch (IndexOutOfBoundsException e) {
throw new ConcurrentModificationException();
}
expectedModCount = modCount;
if (pos == lastPosition) {
pos--;
}
lastPosition = -1;
}
}
private final class FullListIterator extends SimpleListIterator implements ListIterator {
FullListIterator(int start) {
if (start >= 0 && start <= size()) {
pos = start - 1;
} else {
throw new IndexOutOfBoundsException();
}
}
public void add(E object) {
if (expectedModCount == modCount) {
try {
AbstractList.this.add(pos + 1, object);
} catch (IndexOutOfBoundsException e) {
throw new NoSuchElementException();
}
pos++;
lastPosition = -1;
if (modCount != expectedModCount) {
expectedModCount = modCount;
}
} else {
throw new ConcurrentModificationException();
}
}
public boolean hasPrevious() {
return pos >= 0;
}
public int nextIndex() {
return pos + 1;
}
public E previous() {
if (expectedModCount == modCount) {
try {
E result = get(pos);
lastPosition = pos;
pos--;
return result;
} catch (IndexOutOfBoundsException e) {
throw new NoSuchElementException();
}
}
throw new ConcurrentModificationException();
}
public int previousIndex() {
return pos;
}
public void set(E object) {
if (expectedModCount == modCount) {
try {
AbstractList.this.set(lastPosition, object);
} catch (IndexOutOfBoundsException e) {
throw new IllegalStateException();
}
} else {
throw new ConcurrentModificationException();
}
}
}
private static final class SubAbstractListRandomAccess extends
SubAbstractList implements RandomAccess {
SubAbstractListRandomAccess(AbstractList list, int start, int end) {
super(list, start, end);
}
}
private static class SubAbstractList extends AbstractList {
private final AbstractList fullList;
private int offset;
private int size;
private static final class SubAbstractListIterator implements
ListIterator {
private final SubAbstractList subList;
private final ListIterator iterator;
private int start;
private int end;
SubAbstractListIterator(ListIterator it,
SubAbstractList list, int offset, int length) {
iterator = it;
subList = list;
start = offset;
end = start + length;
}
public void add(E object) {
iterator.add(object);
subList.sizeChanged(true);
end++;
}
public boolean hasNext() {
return iterator.nextIndex() < end;
}
public boolean hasPrevious() {
return iterator.previousIndex() >= start;
}
public E next() {
if (iterator.nextIndex() < end) {
return iterator.next();
}
throw new NoSuchElementException();
}
public int nextIndex() {
return iterator.nextIndex() - start;
}
public E previous() {
if (iterator.previousIndex() >= start) {
return iterator.previous();
}
throw new NoSuchElementException();
}
public int previousIndex() {
int previous = iterator.previousIndex();
if (previous >= start) {
return previous - start;
}
return -1;
}
public void remove() {
iterator.remove();
subList.sizeChanged(false);
end--;
}
public void set(E object) {
iterator.set(object);
}
}
SubAbstractList(AbstractList list, int start, int end) {
fullList = list;
modCount = fullList.modCount;
offset = start;
size = end - start;
}
@Override
public void add(int location, E object) {
if (modCount == fullList.modCount) {
if (location >= 0 && location <= size) {
fullList.add(location + offset, object);
size++;
modCount = fullList.modCount;
} else {
throw new IndexOutOfBoundsException();
}
} else {
throw new ConcurrentModificationException();
}
}
@Override
public boolean addAll(int location, Collection collection) {
if (modCount == fullList.modCount) {
if (location >= 0 && location <= size) {
boolean result = fullList.addAll(location + offset,
collection);
if (result) {
size += collection.size();
modCount = fullList.modCount;
}
return result;
}
throw new IndexOutOfBoundsException();
}
throw new ConcurrentModificationException();
}
@Override
public boolean addAll(Collection collection) {
if (modCount == fullList.modCount) {
boolean result = fullList.addAll(offset + size, collection);
if (result) {
size += collection.size();
modCount = fullList.modCount;
}
return result;
}
throw new ConcurrentModificationException();
}
@Override
public E get(int location) {
if (modCount == fullList.modCount) {
if (location >= 0 && location < size) {
return fullList.get(location + offset);
}
throw new IndexOutOfBoundsException();
}
throw new ConcurrentModificationException();
}
@Override
public Iterator iterator() {
return listIterator(0);
}
@Override
public ListIterator listIterator(int location) {
if (modCount == fullList.modCount) {
if (location >= 0 && location <= size) {
return new SubAbstractListIterator(fullList
.listIterator(location + offset), this, offset,
size);
}
throw new IndexOutOfBoundsException();
}
throw new ConcurrentModificationException();
}
@Override
public E remove(int location) {
if (modCount == fullList.modCount) {
if (location >= 0 && location < size) {
E result = fullList.remove(location + offset);
size--;
modCount = fullList.modCount;
return result;
}
throw new IndexOutOfBoundsException();
}
throw new ConcurrentModificationException();
}
@Override
protected void removeRange(int start, int end) {
if (start != end) {
if (modCount == fullList.modCount) {
fullList.removeRange(start + offset, end + offset);
size -= end - start;
modCount = fullList.modCount;
} else {
throw new ConcurrentModificationException();
}
}
}
@Override
public E set(int location, E object) {
if (modCount == fullList.modCount) {
if (location >= 0 && location < size) {
return fullList.set(location + offset, object);
}
throw new IndexOutOfBoundsException();
}
throw new ConcurrentModificationException();
}
@Override
public int size() {
if (modCount == fullList.modCount) {
return size;
}
throw new ConcurrentModificationException();
}
void sizeChanged(boolean increment) {
if (increment) {
size++;
} else {
size--;
}
modCount = fullList.modCount;
}
}
/**
* Constructs a new instance of this AbstractList.
*/
protected AbstractList() {
}
/**
* Inserts the specified object into this List 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 List, the object
* is added at the end.
*
* Concrete implementations that would like to support the add functionality
* must override this method.
*
* @param location
* the index at which to insert.
* @param object
* the object to add.
*
* @throws UnsupportedOperationException
* if adding to this List is not supported.
* @throws ClassCastException
* if the class of the object is inappropriate for this
* List
* @throws IllegalArgumentException
* if the object cannot be added to this List
* @throws IndexOutOfBoundsException
* if {@code location < 0 || location > size()}
*/
public void add(int location, E object) {
throw new UnsupportedOperationException();
}
/**
* Adds the specified object at the end of this List.
*
*
* @param object
* the object to add
* @return true
*
* @throws UnsupportedOperationException
* if adding to this List is not supported
* @throws ClassCastException
* if the class of the object is inappropriate for this
* List
* @throws IllegalArgumentException
* if the object cannot be added to this List
*/
@Override
public boolean add(E object) {
add(size(), object);
return true;
}
/**
* Inserts the objects in the specified Collection at the specified location
* in this List. 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 List is modified, {@code false} otherwise.
* @throws UnsupportedOperationException
* if adding to this list is not supported.
* @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 || location > size()}
*/
public boolean addAll(int location, Collection collection) {
Iterator it = collection.iterator();
while (it.hasNext()) {
add(location++, it.next());
}
return !collection.isEmpty();
}
/**
* Removes all elements from this list, leaving it empty.
*
* @throws UnsupportedOperationException
* if removing from this list is not supported.
* @see List#isEmpty
* @see List#size
*/
@Override
public void clear() {
removeRange(0, size());
}
/**
* Compares the specified object to this list and return true if they are
* equal. Two lists are equal when they both contain the same objects in the
* same order.
*
* @param object
* the object to compare to this object.
* @return {@code true} if the specified object is equal to this list,
* {@code false} otherwise.
* @see #hashCode
*/
@Override
public boolean equals(Object object) {
if (this == object) {
return true;
}
if (object instanceof List) {
List list = (List) object;
if (list.size() != size()) {
return false;
}
Iterator it1 = iterator(), it2 = list.iterator();
while (it1.hasNext()) {
Object e1 = it1.next(), e2 = it2.next();
if (!(e1 == null ? e2 == null : e1.equals(e2))) {
return false;
}
}
return true;
}
return false;
}
/**
* Returns the element at the specified location in this list.
*
* @param location
* the index of the element to return.
* @return the element at the specified index.
* @throws IndexOutOfBoundsException
* if {@code location < 0 || location >= size()}
*/
public abstract E get(int location);
/**
* Returns the hash code of this list. The hash code is calculated by taking
* each element's hashcode into account.
*
* @return the hash code.
* @see #equals
* @see List#hashCode()
*/
@Override
public int hashCode() {
int result = 1;
Iterator it = iterator();
while (it.hasNext()) {
Object object = it.next();
result = (31 * result) + (object == null ? 0 : object.hashCode());
}
return result;
}
/**
* Searches this list for the specified object and returns the index of the
* first occurrence.
*
* @param object
* the object to search for.
* @return the index of the first occurrence of the object, or -1 if it was
* not found.
*/
public int indexOf(Object object) {
ListIterator it = listIterator();
if (object != null) {
while (it.hasNext()) {
if (object.equals(it.next())) {
return it.previousIndex();
}
}
} else {
while (it.hasNext()) {
if (it.next() == null) {
return it.previousIndex();
}
}
}
return -1;
}
/**
* Returns an iterator on the elements of this list. The elements are
* iterated in the same order as they occur in the list.
*
* @return an iterator on the elements of this list.
* @see Iterator
*/
@Override
public Iterator iterator() {
return new SimpleListIterator();
}
/**
* Searches this list 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 the
* object was not found.
*/
public int lastIndexOf(Object object) {
ListIterator it = listIterator(size());
if (object != null) {
while (it.hasPrevious()) {
if (object.equals(it.previous())) {
return it.nextIndex();
}
}
} else {
while (it.hasPrevious()) {
if (it.previous() == null) {
return it.nextIndex();
}
}
}
return -1;
}
/**
* Returns a ListIterator on the elements of this list. The elements are
* iterated in the same order that they occur in the list.
*
* @return a ListIterator on the elements of this list
* @see ListIterator
*/
public ListIterator listIterator() {
return listIterator(0);
}
/**
* Returns a list iterator on the elements of this list. The elements are
* iterated in the same order as they occur in the list. 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 list.
* @throws IndexOutOfBoundsException
* if {@code location < 0 || location > size()}
* @see ListIterator
*/
public ListIterator listIterator(int location) {
return new FullListIterator(location);
}
/**
* Removes the object at the specified location from this list.
*
* @param location
* the index of the object to remove.
* @return the removed object.
* @throws UnsupportedOperationException
* if removing from this list is not supported.
* @throws IndexOutOfBoundsException
* if {@code location < 0 || location >= size()}
*/
public E remove(int location) {
throw new UnsupportedOperationException();
}
/**
* Removes the objects in the specified range from the start to the end
* index minus one.
*
* @param start
* the index at which to start removing.
* @param end
* the index after the last element to remove.
* @throws UnsupportedOperationException
* if removing from this list is not supported.
* @throws IndexOutOfBoundsException
* if {@code start < 0} or {@code start >= size()}.
*/
protected void removeRange(int start, int end) {
Iterator it = listIterator(start);
for (int i = start; i < end; i++) {
it.next();
it.remove();
}
}
/**
* Replaces the element at the specified location in this list 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 UnsupportedOperationException
* if replacing elements in this list is not supported.
* @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 || location >= size()}
*/
public E set(int location, E object) {
throw new UnsupportedOperationException();
}
/**
* Returns a part of consecutive elements of this list as a view. The
* returned view will be of zero length if start equals end. Any change that
* occurs in the returned subList will be reflected to the original list,
* and vice-versa. All the supported optional operations by the original
* list will also be supported by this subList.
*
* This method can be used as a handy method to do some operations on a sub
* range of the original list, for example
* {@code list.subList(from, to).clear();}
*
* If the original list is modified in other ways than through the returned
* subList, the behavior of the returned subList becomes undefined.
*
* The returned subList is a subclass of AbstractList. The subclass stores
* offset, size of itself, and modCount of the original list. If the
* original list implements RandomAccess interface, the returned subList
* also implements RandomAccess interface.
*
* The subList's set(int, Object), get(int), add(int, Object), remove(int),
* addAll(int, Collection) and removeRange(int, int) methods first check the
* bounds, adjust offsets and then call the corresponding methods of the
* original AbstractList. addAll(Collection c) method of the returned
* subList calls the original addAll(offset + size, c).
*
* The listIterator(int) method of the subList wraps the original list
* iterator. The iterator() method of the subList invokes the original
* listIterator() method, and the size() method merely returns the size of
* the subList.
*
* All methods will throw a ConcurrentModificationException if the modCount
* of the original list is not equal to the expected value.
*
* @param start
* start index of the subList (inclusive).
* @param end
* end index of the subList, (exclusive).
* @return a subList view of this list starting from {@code start}
* (inclusive), and ending with {@code end} (exclusive)
* @throws IndexOutOfBoundsException
* if (start < 0 || end > size())
* @throws IllegalArgumentException
* if (start > end)
*/
public List subList(int start, int end) {
if (start >= 0 && end <= size()) {
if (start <= end) {
if (this instanceof RandomAccess) {
return new SubAbstractListRandomAccess(this, start, end);
}
return new SubAbstractList(this, start, end);
}
throw new IllegalArgumentException();
}
throw new IndexOutOfBoundsException();
}
}