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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.
*/
package java.util;
/**
* ArrayList is an implementation of {@link List}, backed by an array. All
* optional operations adding, removing, and replacing are supported. The
* elements can be any objects.
*
* @since 1.2
*/
public class ArrayList extends AbstractList implements List, RandomAccess {
private static final long serialVersionUID = 8683452581122892189L;
private transient int firstIndex;
private transient int size;
private transient E[] array;
/**
* Constructs a new instance of {@code ArrayList} with ten capacity.
*/
public ArrayList() {
this(10);
}
/**
* Constructs a new instance of {@code ArrayList} with the specified
* capacity.
*
* @param capacity
* the initial capacity of this {@code ArrayList}.
*/
public ArrayList(int capacity) {
if (capacity < 0) {
throw new IllegalArgumentException();
}
firstIndex = size = 0;
array = newElementArray(capacity);
}
/**
* Constructs a new instance of {@code ArrayList} containing the elements of
* the specified collection. The initial size of the {@code ArrayList} will
* be 10% larger than the size of the specified collection.
*
* @param collection
* the collection of elements to add.
*/
public ArrayList(Collection collection) {
firstIndex = 0;
Object[] objects = toObjectArray(collection);
size = objects.length;
// REVIEW: Created 2 array copies of the original collection here
// Could be better to use the collection iterator and
// copy once?
array = newElementArray(size + (size / 10));
System.arraycopy(objects, 0, array, 0, size);
modCount = 1;
}
static void toObjectArray(Object[] objects, Collection collection) {
Iterator i = collection.iterator();
for(int iter = 0 ; iter < objects.length ; iter++) {
objects[iter] = i.next();
}
}
static Object[] toObjectArray(Collection collection) {
Object[] objects = new Object[collection.size()];
toObjectArray(objects, collection);
return objects;
}
@SuppressWarnings("unchecked")
private E[] newElementArray(int size) {
return (E[]) new Object[size];
}
/**
* Inserts the specified object into this {@code ArrayList} at the specified
* location. The object is inserted before any previous element at the
* specified location. If the location is equal to the size of this
* {@code ArrayList}, the object is added at the end.
*
* @param location
* the index at which to insert the object.
* @param object
* the object to add.
* @throws IndexOutOfBoundsException
* when {@code location < 0 || > size()}
*/
@Override
public void add(int location, E object) {
if (location < 0 || location > size) {
throw new IndexOutOfBoundsException("" + location + " out of: " + size);
}
if (location == 0) {
if (firstIndex == 0) {
growAtFront(1);
}
array[--firstIndex] = object;
} else if (location == size) {
if (firstIndex + size == array.length) {
growAtEnd(1);
}
array[firstIndex + size] = object;
} else { // must be case: (0 < location && location < size)
if (size == array.length) {
growForInsert(location, 1);
} else if (firstIndex + size == array.length
|| (firstIndex > 0 && location < size / 2)) {
System.arraycopy(array, firstIndex, array, --firstIndex,
location);
} else {
int index = location + firstIndex;
System.arraycopy(array, index, array, index + 1, size
- location);
}
array[location + firstIndex] = object;
}
size++;
modCount++;
}
/**
* Adds the specified object at the end of this {@code ArrayList}.
*
* @param object
* the object to add.
* @return always true
*/
@Override
public boolean add(E object) {
if (firstIndex + size == array.length) {
growAtEnd(1);
}
array[firstIndex + size] = object;
size++;
modCount++;
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 {@code ArrayList} is modified, {@code false}
* otherwise.
* @throws IndexOutOfBoundsException
* when {@code location < 0 || > size()}
*/
@Override
public boolean addAll(int location, Collection collection) {
if (location < 0 || location > size) {
throw new IndexOutOfBoundsException("" + location + " out of: " + size);
}
Object[] dumparray = toObjectArray(collection);
int growSize = dumparray.length;
// REVIEW: Why do this check here rather than check
// collection.size() earlier? RI behaviour?
if (growSize == 0) {
return false;
}
if (location == 0) {
growAtFront(growSize);
firstIndex -= growSize;
} else if (location == size) {
if (firstIndex + size > array.length - growSize) {
growAtEnd(growSize);
}
} else { // must be case: (0 < location && location < size)
if (array.length - size < growSize) {
growForInsert(location, growSize);
} else if (firstIndex + size > array.length - growSize
|| (firstIndex > 0 && location < size / 2)) {
int newFirst = firstIndex - growSize;
if (newFirst < 0) {
int index = location + firstIndex;
System.arraycopy(array, index, array, index - newFirst,
size - location);
newFirst = 0;
}
System.arraycopy(array, firstIndex, array, newFirst, location);
firstIndex = newFirst;
} else {
int index = location + firstIndex;
System.arraycopy(array, index, array, index + growSize, size
- location);
}
}
System.arraycopy(dumparray, 0, this.array, location + firstIndex,
growSize);
size += growSize;
modCount++;
return true;
}
/**
* Adds the objects in the specified collection to this {@code ArrayList}.
*
* @param collection
* the collection of objects.
* @return {@code true} if this {@code ArrayList} is modified, {@code false}
* otherwise.
*/
@Override
public boolean addAll(Collection collection) {
Object[] dumpArray = toObjectArray(collection);
if (dumpArray.length == 0) {
return false;
}
if (dumpArray.length > array.length - (firstIndex + size)) {
growAtEnd(dumpArray.length);
}
System.arraycopy(dumpArray, 0, this.array, firstIndex + size,
dumpArray.length);
size += dumpArray.length;
modCount++;
return true;
}
/**
* Removes all elements from this {@code ArrayList}, leaving it empty.
*
* @see #isEmpty
* @see #size
*/
@Override
public void clear() {
if (size != 0) {
// REVIEW: Should we use Arrays.fill() instead of just
// allocating a new array? Should we use the same
// sized array?
Arrays.fill(array, firstIndex, firstIndex + size, null);
// REVIEW: Should the indexes point into the middle of the
// array rather than 0?
firstIndex = size = 0;
modCount++;
}
}
/**
* Searches this {@code ArrayList} for the specified object.
*
* @param object
* the object to search for.
* @return {@code true} if {@code object} is an element of this
* {@code ArrayList}, {@code false} otherwise
*/
@Override
public boolean contains(Object object) {
int lastIndex = firstIndex + size;
if (object != null) {
for (int i = firstIndex; i < lastIndex; i++) {
if (object.equals(array[i])) {
return true;
}
}
} else {
for (int i = firstIndex; i < lastIndex; i++) {
if (array[i] == null) {
return true;
}
}
}
return false;
}
/**
* Ensures that after this operation the {@code ArrayList} can hold the
* specified number of elements without further growing.
*
* @param minimumCapacity
* the minimum capacity asked for.
*/
public void ensureCapacity(int minimumCapacity) {
int required = minimumCapacity - array.length;
if (required > 0) {
// REVIEW: Why do we check the firstIndex first? Growing
// the end makes more sense
if (firstIndex > 0) {
growAtFront(required);
} else {
growAtEnd(required);
}
}
}
@Override
public E get(int location) {
if (location < 0 || location >= size) {
throw new IndexOutOfBoundsException("" + location + " out of: " + size);
}
return array[firstIndex + location];
}
private void growAtEnd(int required) {
if (array.length - size >= required) {
// REVIEW: as growAtEnd, why not move size == 0 out as
// special case
if (size != 0) {
System.arraycopy(array, firstIndex, array, 0, size);
int start = size < firstIndex ? firstIndex : size;
// REVIEW: I think we null too much
// array.length should be lastIndex ?
Arrays.fill(array, start, array.length, null);
}
firstIndex = 0;
} else {
// REVIEW: If size is 0?
// Does size/2 seems a little high!
int increment = size / 2;
if (required > increment) {
increment = required;
}
if (increment < 12) {
increment = 12;
}
E[] newArray = newElementArray(size + increment);
if (size != 0) {
System.arraycopy(array, firstIndex, newArray, 0, size);
firstIndex = 0;
}
array = newArray;
}
}
private void growAtFront(int required) {
if (array.length - size >= required) {
int newFirst = array.length - size;
// REVIEW: as growAtEnd, why not move size == 0 out as
// special case
if (size != 0) {
System.arraycopy(array, firstIndex, array, newFirst, size);
int lastIndex = firstIndex + size;
int length = lastIndex > newFirst ? newFirst : lastIndex;
Arrays.fill(array, firstIndex, length, null);
}
firstIndex = newFirst;
} else {
int increment = size / 2;
if (required > increment) {
increment = required;
}
if (increment < 12) {
increment = 12;
}
E[] newArray = newElementArray(size + increment);
if (size != 0) {
System.arraycopy(array, firstIndex, newArray, increment, size);
}
firstIndex = newArray.length - size;
array = newArray;
}
}
private void growForInsert(int location, int required) {
// REVIEW: we grow too quickly because we are called with the
// size of the new collection to add without taking in
// to account the free space we already have
int increment = size / 2;
if (required > increment) {
increment = required;
}
if (increment < 12) {
increment = 12;
}
E[] newArray = newElementArray(size + increment);
// REVIEW: biased towards leaving space at the beginning?
// perhaps newFirst should be (increment-required)/2?
int newFirst = increment - required;
// Copy elements after location to the new array skipping inserted
// elements
System.arraycopy(array, location + firstIndex, newArray, newFirst
+ location + required, size - location);
// Copy elements before location to the new array from firstIndex
System.arraycopy(array, firstIndex, newArray, newFirst, location);
firstIndex = newFirst;
array = newArray;
}
@Override
public int indexOf(Object object) {
// REVIEW: should contains call this method?
int lastIndex = firstIndex + size;
if (object != null) {
for (int i = firstIndex; i < lastIndex; i++) {
if (object.equals(array[i])) {
return i - firstIndex;
}
}
} else {
for (int i = firstIndex; i < lastIndex; i++) {
if (array[i] == null) {
return i - firstIndex;
}
}
}
return -1;
}
@Override
public boolean isEmpty() {
return size == 0;
}
@Override
public int lastIndexOf(Object object) {
int lastIndex = firstIndex + size;
if (object != null) {
for (int i = lastIndex - 1; i >= firstIndex; i--) {
if (object.equals(array[i])) {
return i - firstIndex;
}
}
} else {
for (int i = lastIndex - 1; i >= firstIndex; i--) {
if (array[i] == null) {
return i - firstIndex;
}
}
}
return -1;
}
/**
* Removes the object at the specified location from this list.
*
* @param location
* the index of the object to remove.
* @return the removed object.
* @throws IndexOutOfBoundsException
* when {@code location < 0 || >= size()}
*/
@Override
public E remove(int location) {
E result;
if (location < 0 || location >= size) {
throw new IndexOutOfBoundsException("" + location + " out of: " + size);
}
if (location == 0) {
result = array[firstIndex];
array[firstIndex++] = null;
} else if (location == size - 1) {
int lastIndex = firstIndex + size - 1;
result = array[lastIndex];
array[lastIndex] = null;
} else {
int elementIndex = firstIndex + location;
result = array[elementIndex];
if (location < size / 2) {
System.arraycopy(array, firstIndex, array, firstIndex + 1,
location);
array[firstIndex++] = null;
} else {
System.arraycopy(array, elementIndex + 1, array,
elementIndex, size - location - 1);
array[firstIndex+size-1] = null;
}
}
size--;
// REVIEW: we can move this to the first if case since it
// can only occur when size==1
if (size == 0) {
firstIndex = 0;
}
modCount++;
return result;
}
@Override
public boolean remove(Object object) {
int location = indexOf(object);
if (location >= 0) {
remove(location);
return true;
}
return false;
}
/**
* Removes the objects in the specified range from the start to the end, but
* not including the end index.
*
* @param start
* the index at which to start removing.
* @param end
* the index one after the end of the range to remove.
* @throws IndexOutOfBoundsException
* when {@code start < 0, start > end} or {@code end > size()}
*/
@Override
protected void removeRange(int start, int end) {
// REVIEW: does RI call this from remove(location)
if (start < 0) {
throw new IndexOutOfBoundsException("" + start);
} else if (end > size) {
throw new IndexOutOfBoundsException("" + end + " out of: " + size);
} else if (start > end) {
throw new IndexOutOfBoundsException("" + start + " out of: " + end);
}
if (start == end) {
return;
}
if (end == size) {
Arrays.fill(array, firstIndex + start, firstIndex + size, null);
} else if (start == 0) {
Arrays.fill(array, firstIndex, firstIndex + end, null);
firstIndex += end;
} else {
// REVIEW: should this optimize to do the smallest copy?
System.arraycopy(array, firstIndex + end, array, firstIndex
+ start, size - end);
int lastIndex = firstIndex + size;
int newLast = lastIndex + start - end;
Arrays.fill(array, newLast, lastIndex, null);
}
size -= end - start;
modCount++;
}
/**
* Replaces the element at the specified location in this {@code ArrayList}
* 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 IndexOutOfBoundsException
* when {@code location < 0 || >= size()}
*/
@Override
public E set(int location, E object) {
if (location < 0 || location >= size) {
throw new IndexOutOfBoundsException("" + location + " out of: " + size);
}
E result = array[firstIndex + location];
array[firstIndex + location] = object;
return result;
}
/**
* Returns the number of elements in this {@code ArrayList}.
*
* @return the number of elements in this {@code ArrayList}.
*/
@Override
public int size() {
return size;
}
/**
* Returns a new array containing all elements contained in this
* {@code ArrayList}.
*
* @return an array of the elements from this {@code ArrayList}
*/
@Override
public Object[] toArray() {
Object[] result = new Object[size];
System.arraycopy(array, firstIndex, result, 0, size);
return result;
}
/**
* Returns an array containing all elements contained in this
* {@code ArrayList}. If the specified array is large enough to hold the
* elements, the specified array is used, otherwise an array of the same
* type is created. If the specified array is used and is larger than this
* {@code ArrayList}, the array element following the collection elements
* is set to null.
*
* @param contents
* the array.
* @return an array of the elements from this {@code ArrayList}.
* @throws ArrayStoreException
* when the type of an element in this {@code ArrayList} cannot
* be stored in the type of the specified array.
*/
@Override
@SuppressWarnings("unchecked")
public T[] toArray(T[] contents) {
Object[] arr = contents;
if (size > arr.length) {
arr = new Object[size];
}
System.arraycopy(array, firstIndex, arr, 0, size);
if (size < arr.length) {
// REVIEW: do we use this incorrectly - i.e. do we null
// the rest out?
arr[size] = null;
}
return (T[])arr;
}
/**
* Sets the capacity of this {@code ArrayList} to be the same as the current
* size.
*
* @see #size
*/
public void trimToSize() {
E[] newArray = newElementArray(size);
System.arraycopy(array, firstIndex, newArray, 0, size);
array = newArray;
firstIndex = 0;
modCount = 0;
}
}