it.unimi.dsi.fastutil.objects.ObjectArrayList Maven / Gradle / Ivy
/*
* Copyright (C) 2002-2017 Sebastiano Vigna
*
* Licensed 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 it.unimi.dsi.fastutil.objects;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.RandomAccess;
import java.util.NoSuchElementException;
/** A type-specific array-based list; provides some additional methods that use polymorphism to avoid (un)boxing.
*
* This class implements a lightweight, fast, open, optimized,
* reuse-oriented version of array-based lists. Instances of this class
* represent a list with an array that is enlarged as needed when new entries
* are created (by doubling the current length), but is
* never made smaller (even on a {@link #clear()}). A family of
* {@linkplain #trim() trimming methods} lets you control the size of the
* backing array; this is particularly useful if you reuse instances of this class.
* Range checks are equivalent to those of {@link java.util}'s classes, but
* they are delayed as much as possible.
*
*
The backing array is exposed by the {@link #elements()} method. If an instance
* of this class was created {@linkplain #wrap(Object[],int) by wrapping},
* backing-array reallocations will be performed using reflection, so that
* {@link #elements()} can return an array of the same type of the original array: the comments
* about efficiency made in {@link it.unimi.dsi.fastutil.objects.ObjectArrays} apply here.
* Moreover, you must take into consideration that assignment to an array
* not of type {@code Object[]} is slower due to type checking.
*
*
This class implements the bulk methods removeElements(),
* addElements() and getElements() using
* high-performance system calls (e.g., {@link
* System#arraycopy(Object,int,Object,int,int) System.arraycopy()} instead of
* expensive loops.
*
* @see java.util.ArrayList
*/
public class ObjectArrayList extends AbstractObjectList implements RandomAccess, Cloneable, java.io.Serializable {
private static final long serialVersionUID = -7046029254386353131L;
/** The initial default capacity of an array list. */
public final static int DEFAULT_INITIAL_CAPACITY = 16;
/** Whether the backing array was passed to wrap(). In
* this case, we must reallocate with the same type of array. */
protected final boolean wrapped;
/** The backing array. */
protected transient K a[];
/** The current actual size of the list (never greater than the backing-array length). */
protected int size;
private static final boolean ASSERTS = false;
/** Creates a new array list using a given array.
*
* This constructor is only meant to be used by the wrapping methods.
*
* @param a the array that will be used to back this array list.
*/
protected ObjectArrayList(final K a[], boolean dummy) {
this.a = a;
this.wrapped = true;
}
/** Creates a new array list with given capacity.
*
* @param capacity the initial capacity of the array list (may be 0).
*/
@SuppressWarnings("unchecked")
public ObjectArrayList(final int capacity) {
if (capacity < 0) throw new IllegalArgumentException("Initial capacity (" + capacity + ") is negative");
a = (K[]) new Object[capacity];
wrapped = false;
}
/** Creates a new array list with {@link #DEFAULT_INITIAL_CAPACITY} capacity.
*/
public ObjectArrayList() {
this(DEFAULT_INITIAL_CAPACITY);
}
/** Creates a new array list and fills it with a given collection.
*
* @param c a collection that will be used to fill the array list.
*/
public ObjectArrayList(final Collection c) {
this(c.size());
size = ObjectIterators.unwrap(c.iterator(), a);
}
/** Creates a new array list and fills it with a given type-specific collection.
*
* @param c a type-specific collection that will be used to fill the array list.
*/
public ObjectArrayList(final ObjectCollection c) {
this(c.size());
size = ObjectIterators.unwrap(c.iterator(), a);
}
/** Creates a new array list and fills it with a given type-specific list.
*
* @param l a type-specific list that will be used to fill the array list.
*/
public ObjectArrayList(final ObjectList l) {
this(l.size());
l.getElements(0, a, 0, size = l.size());
}
/** Creates a new array list and fills it with the elements of a given array.
*
* @param a an array whose elements will be used to fill the array list.
*/
public ObjectArrayList(final K a[]) {
this(a, 0, a.length);
}
/** Creates a new array list and fills it with the elements of a given array.
*
* @param a an array whose elements will be used to fill the array list.
* @param offset the first element to use.
* @param length the number of elements to use.
*/
public ObjectArrayList(final K a[], final int offset, final int length) {
this(length);
System.arraycopy(a, offset, this.a, 0, length);
size = length;
}
/** Creates a new array list and fills it with the elements returned by an iterator..
*
* @param i an iterator whose returned elements will fill the array list.
*/
public ObjectArrayList(final Iterator i) {
this();
while(i.hasNext()) this.add((i.next()));
}
/** Creates a new array list and fills it with the elements returned by a type-specific iterator..
*
* @param i a type-specific iterator whose returned elements will fill the array list.
*/
public ObjectArrayList(final ObjectIterator i) {
this();
while(i.hasNext()) this.add(i.next());
}
/** Returns the backing array of this list.
*
*
If this array list was created by wrapping a given array, it is guaranteed
* that the type of the returned array will be the same. Otherwise, the returned
* array will be of type {@link Object Object[]} (in spite of the declared return type).
*
*
Warning: This behaviour may cause (unfathomable)
* run-time errors if a method expects an array
* actually of type K[], but this methods returns an array
* of type {@link Object Object[]}.
*
* @return the backing array.
*/
public K[] elements() {
return a;
}
/** Wraps a given array into an array list of given size.
*
*
Note it is guaranteed
* that the type of the array returned by {@link #elements()} will be the same
* (see the comments in the class documentation).
*
* @param a an array to wrap.
* @param length the length of the resulting array list.
* @return a new array list of the given size, wrapping the given array.
*/
public static ObjectArrayList wrap(final K a[], final int length) {
if (length > a.length) throw new IllegalArgumentException("The specified length (" + length + ") is greater than the array size (" + a.length + ")");
final ObjectArrayList l = new ObjectArrayList (a, false);
l.size = length;
return l;
}
/** Wraps a given array into an array list.
*
* Note it is guaranteed
* that the type of the array returned by {@link #elements()} will be the same
* (see the comments in the class documentation).
*
* @param a an array to wrap.
* @return a new array list wrapping the given array.
*/
public static ObjectArrayList wrap(final K a[]) {
return wrap(a, a.length);
}
/** Ensures that this array list can contain the given number of entries without resizing.
*
* @param capacity the new minimum capacity for this array list.
*/
@SuppressWarnings("unchecked")
public void ensureCapacity(final int capacity) {
if (wrapped) a = ObjectArrays.ensureCapacity(a, capacity, size);
else {
if (capacity > a.length) {
final Object t[] = new Object[capacity];
System.arraycopy(a, 0, t, 0, size);
a = (K[])t;
}
}
if (ASSERTS) assert size <= a.length;
}
/** Grows this array list, ensuring that it can contain the given number of entries without resizing,
* and in case enlarging it at least by a factor of two.
*
* @param capacity the new minimum capacity for this array list.
*/
@SuppressWarnings("unchecked")
private void grow(final int capacity) {
if (wrapped) a = ObjectArrays.grow(a, capacity, size);
else {
if (capacity > a.length) {
final int newLength = (int)Math.max(Math.min(2L * a.length, it.unimi.dsi.fastutil.Arrays.MAX_ARRAY_SIZE), capacity);
final Object t[] = new Object[newLength];
System.arraycopy(a, 0, t, 0, size);
a = (K[])t;
}
}
if (ASSERTS) assert size <= a.length;
}
@Override
public void add(final int index, final K k) {
ensureIndex(index);
grow(size + 1);
if (index != size) System.arraycopy(a, index, a, index + 1, size - index);
a[index] = k;
size++;
if (ASSERTS) assert size <= a.length;
}
@Override
public boolean add(final K k) {
grow(size + 1);
a[size++] = k;
if (ASSERTS) assert size <= a.length;
return true;
}
@Override
public K get(final int index) {
if (index >= size) throw new IndexOutOfBoundsException("Index (" + index + ") is greater than or equal to list size (" + size + ")");
return a[index];
}
@Override
public int indexOf(final Object k) {
for(int i = 0; i < size; i++) if (( (k) == null ? (a[i]) == null : (k).equals(a[i]) )) return i;
return -1;
}
@Override
public int lastIndexOf(final Object k) {
for(int i = size; i-- != 0;) if (( (k) == null ? (a[i]) == null : (k).equals(a[i]) )) return i;
return -1;
}
@Override
public K remove(final int index) {
if (index >= size) throw new IndexOutOfBoundsException("Index (" + index + ") is greater than or equal to list size (" + size + ")");
final K old = a[index];
size--;
if (index != size) System.arraycopy(a, index + 1, a, index, size - index);
a[size] = null;
if (ASSERTS) assert size <= a.length;
return old;
}
@Override
public boolean remove(final Object k) {
int index = indexOf(k);
if (index == -1) return false;
remove(index);
if (ASSERTS) assert size <= a.length;
return true;
}
@Override
public K set(final int index, final K k) {
if (index >= size) throw new IndexOutOfBoundsException("Index (" + index + ") is greater than or equal to list size (" + size + ")");
K old = a[index];
a[index] = k;
return old;
}
@Override
public void clear() {
Arrays.fill(a, 0, size, null);
size = 0;
if (ASSERTS) assert size <= a.length;
}
@Override
public int size() {
return size;
}
@Override
public void size(final int size) {
if (size > a.length) ensureCapacity(size);
if (size > this.size) Arrays.fill(a, this.size, size, (null));
else Arrays.fill(a, size, this.size, (null));
this.size = size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
/** Trims this array list so that the capacity is equal to the size.
*
* @see java.util.ArrayList#trimToSize()
*/
public void trim() {
trim(0);
}
/** Trims the backing array if it is too large.
*
* If the current array length is smaller than or equal to
* n, this method does nothing. Otherwise, it trims the
* array length to the maximum between n and {@link #size()}.
*
* This method is useful when reusing lists. {@linkplain #clear() Clearing a
* list} leaves the array length untouched. If you are reusing a list
* many times, you can call this method with a typical
* size to avoid keeping around a very large array just
* because of a few large transient lists.
*
* @param n the threshold for the trimming.
*/
@SuppressWarnings("unchecked")
public void trim(final int n) {
// TODO: use Arrays.trim() and preserve type only if necessary
if (n >= a.length || size == a.length) return;
final K t[] = (K[]) new Object[Math.max(n, size)];
System.arraycopy(a, 0, t, 0, size);
a = t;
if (ASSERTS) assert size <= a.length;
}
/** Copies element of this type-specific list into the given array using optimized system calls.
*
* @param from the start index (inclusive).
* @param a the destination array.
* @param offset the offset into the destination array where to store the first element copied.
* @param length the number of elements to be copied.
*/
@Override
public void getElements(final int from, final Object[] a, final int offset, final int length) {
ObjectArrays.ensureOffsetLength(a, offset, length);
System.arraycopy(this.a, from, a, offset, length);
}
/** Removes elements of this type-specific list using optimized system calls.
*
* @param from the start index (inclusive).
* @param to the end index (exclusive).
*/
@Override
public void removeElements(final int from, final int to) {
it.unimi.dsi.fastutil.Arrays.ensureFromTo(size, from, to);
System.arraycopy(a, to, a, from, size - to);
size -= (to - from);
int i = to - from;
while(i-- != 0) a[size + i] = null;
}
/** Adds elements to this type-specific list using optimized system calls.
*
* @param index the index at which to add elements.
* @param a the array containing the elements.
* @param offset the offset of the first element to add.
* @param length the number of elements to add.
*/
@Override
public void addElements(final int index, final K a[], final int offset, final int length) {
ensureIndex(index);
ObjectArrays.ensureOffsetLength(a, offset, length);
grow(size + length);
System.arraycopy(this.a, index, this.a, index + length, size - index);
System.arraycopy(a, offset, this.a, index, length);
size += length;
}
@Override
public boolean removeAll(final Collection c) {
final Object[] a = this.a;
int j = 0;
for(int i = 0; i < size; i++)
if (! c.contains((a[i]))) a[j++] = a[i];
Arrays.fill(a, j, size, null);
final boolean modified = size != j;
size = j;
return modified;
}
@Override
public ObjectListIterator listIterator(final int index) {
ensureIndex(index);
return new AbstractObjectListIterator () {
int pos = index, last = -1;
public boolean hasNext() { return pos < size; }
public boolean hasPrevious() { return pos > 0; }
public K next() { if (! hasNext()) throw new NoSuchElementException(); return a[last = pos++]; }
public K previous() { if (! hasPrevious()) throw new NoSuchElementException(); return a[last = --pos]; }
public int nextIndex() { return pos; }
public int previousIndex() { return pos - 1; }
public void add(K k) {
ObjectArrayList.this.add(pos++, k);
last = -1;
}
public void set(K k) {
if (last == -1) throw new IllegalStateException();
ObjectArrayList.this.set(last, k);
}
public void remove() {
if (last == -1) throw new IllegalStateException();
ObjectArrayList.this.remove(last);
/* If the last operation was a next(), we are removing an element *before* us, and we must decrease pos correspondingly. */
if (last < pos) pos--;
last = -1;
}
};
}
@Override
public ObjectArrayList clone() {
ObjectArrayList c = new ObjectArrayList (size);
System.arraycopy(a, 0, c.a, 0, size);
c.size = size;
return c;
}
private boolean valEquals(final K a, final K b) {
return a == null ? b == null : a.equals(b);
}
/** Compares this type-specific array list to another one.
*
* This method exists only for sake of efficiency. The implementation
* inherited from the abstract implementation would already work.
*
* @param l a type-specific array list.
* @return true if the argument contains the same elements of this type-specific array list.
*/
public boolean equals(final ObjectArrayList l) {
if (l == this) return true;
int s = size();
if (s != l.size()) return false;
final K[] a1 = a;
final K[] a2 = l.a;
while(s-- != 0) if (! valEquals(a1[s], a2[s])) return false;
return true;
}
/** Compares this array list to another array list.
*
* This method exists only for sake of efficiency. The implementation
* inherited from the abstract implementation would already work.
*
* @param l an array list.
* @return a negative integer,
* zero, or a positive integer as this list is lexicographically less than, equal
* to, or greater than the argument.
*/
@SuppressWarnings("unchecked")
public int compareTo(final ObjectArrayList l) {
final int s1 = size(), s2 = l.size();
final K a1[] = a, a2[] = l.a;
K e1, e2;
int r, i;
for(i = 0; i < s1 && i < s2; i++) {
e1 = a1[i];
e2 = a2[i];
if ((r = ( ((Comparable)(e1)).compareTo(e2) )) != 0) return r;
}
return i < s2 ? -1 : (i < s1 ? 1 : 0);
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
s.defaultWriteObject();
for(int i = 0; i < size; i++) s.writeObject(a[i]);
}
@SuppressWarnings("unchecked")
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
a = (K[]) new Object[size];
for(int i = 0; i < size; i++) a[i] = (K) s.readObject();
}
}