--- jsr166/src/main/java/util/ArrayDeque.java 2005/09/16 23:11:13 1.20
+++ jsr166/src/main/java/util/ArrayDeque.java 2013/01/16 15:06:10 1.41
@@ -1,11 +1,42 @@
/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
* Written by Josh Bloch of Google Inc. and released to the public domain,
- * as explained at http://creativecommons.org/licenses/publicdomain.
+ * as explained at http://creativecommons.org/publicdomain/zero/1.0/.
*/
package java.util;
-import java.util.*; // for javadoc (till 6280605 is fixed)
-import java.io.*;
+import java.util.Spliterator;
+import java.util.stream.Stream;
+import java.util.stream.Streams;
+import java.util.function.Block;
/**
* Resizable-array implementation of the {@link Deque} interface. Array
@@ -45,7 +76,7 @@ import java.io.*;
* Iterator} interfaces.
*
*
This class is a member of the
- *
+ *
* Java Collections Framework.
*
* @author Josh Bloch and Doug Lea
@@ -53,7 +84,7 @@ import java.io.*;
* @param the type of elements held in this collection
*/
public class ArrayDeque extends AbstractCollection
- implements Deque, Cloneable, Serializable
+ implements Deque, Cloneable, java.io.Serializable
{
/**
* The array in which the elements of the deque are stored.
@@ -65,20 +96,20 @@ public class ArrayDeque extends Abstr
* other. We also guarantee that all array cells not holding
* deque elements are always null.
*/
- private transient E[] elements;
+ transient Object[] elements; // non-private to simplify nested class access
/**
* The index of the element at the head of the deque (which is the
* element that would be removed by remove() or pop()); or an
* arbitrary number equal to tail if the deque is empty.
*/
- private transient int head;
+ transient int head;
/**
* The index at which the next element would be added to the tail
* of the deque (via addLast(E), add(E), or push(E)).
*/
- private transient int tail;
+ transient int tail;
/**
* The minimum capacity that we'll use for a newly created deque.
@@ -89,7 +120,7 @@ public class ArrayDeque extends Abstr
// ****** Array allocation and resizing utilities ******
/**
- * Allocate empty array to hold the given number of elements.
+ * Allocates empty array to hold the given number of elements.
*
* @param numElements the number of elements to hold
*/
@@ -109,11 +140,11 @@ public class ArrayDeque extends Abstr
if (initialCapacity < 0) // Too many elements, must back off
initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
}
- elements = (E[]) new Object[initialCapacity];
+ elements = new Object[initialCapacity];
}
/**
- * Double the capacity of this deque. Call only when full, i.e.,
+ * Doubles the capacity of this deque. Call only when full, i.e.,
* when head and tail have wrapped around to become equal.
*/
private void doubleCapacity() {
@@ -127,7 +158,7 @@ public class ArrayDeque extends Abstr
Object[] a = new Object[newCapacity];
System.arraycopy(elements, p, a, 0, r);
System.arraycopy(elements, 0, a, r, p);
- elements = (E[])a;
+ elements = a;
head = 0;
tail = n;
}
@@ -155,7 +186,7 @@ public class ArrayDeque extends Abstr
* sufficient to hold 16 elements.
*/
public ArrayDeque() {
- elements = (E[]) new Object[16];
+ elements = new Object[16];
}
/**
@@ -221,7 +252,7 @@ public class ArrayDeque extends Abstr
* Inserts the specified element at the front of this deque.
*
* @param e the element to add
- * @return true (as specified by {@link Deque#offerFirst})
+ * @return {@code true} (as specified by {@link Deque#offerFirst})
* @throws NullPointerException if the specified element is null
*/
public boolean offerFirst(E e) {
@@ -233,7 +264,7 @@ public class ArrayDeque extends Abstr
* Inserts the specified element at the end of this deque.
*
* @param e the element to add
- * @return true (as specified by {@link Deque#offerLast})
+ * @return {@code true} (as specified by {@link Deque#offerLast})
* @throws NullPointerException if the specified element is null
*/
public boolean offerLast(E e) {
@@ -263,7 +294,9 @@ public class ArrayDeque extends Abstr
public E pollFirst() {
int h = head;
- E result = elements[h]; // Element is null if deque empty
+ @SuppressWarnings("unchecked")
+ E result = (E) elements[h];
+ // Element is null if deque empty
if (result == null)
return null;
elements[h] = null; // Must null out slot
@@ -273,7 +306,8 @@ public class ArrayDeque extends Abstr
public E pollLast() {
int t = (tail - 1) & (elements.length - 1);
- E result = elements[t];
+ @SuppressWarnings("unchecked")
+ E result = (E) elements[t];
if (result == null)
return null;
elements[t] = null;
@@ -285,48 +319,53 @@ public class ArrayDeque extends Abstr
* @throws NoSuchElementException {@inheritDoc}
*/
public E getFirst() {
- E x = elements[head];
- if (x == null)
+ @SuppressWarnings("unchecked")
+ E result = (E) elements[head];
+ if (result == null)
throw new NoSuchElementException();
- return x;
+ return result;
}
/**
* @throws NoSuchElementException {@inheritDoc}
*/
public E getLast() {
- E x = elements[(tail - 1) & (elements.length - 1)];
- if (x == null)
+ @SuppressWarnings("unchecked")
+ E result = (E) elements[(tail - 1) & (elements.length - 1)];
+ if (result == null)
throw new NoSuchElementException();
- return x;
+ return result;
}
+ @SuppressWarnings("unchecked")
public E peekFirst() {
- return elements[head]; // elements[head] is null if deque empty
+ // elements[head] is null if deque empty
+ return (E) elements[head];
}
+ @SuppressWarnings("unchecked")
public E peekLast() {
- return elements[(tail - 1) & (elements.length - 1)];
+ return (E) elements[(tail - 1) & (elements.length - 1)];
}
/**
* Removes the first occurrence of the specified element in this
* deque (when traversing the deque from head to tail).
* If the deque does not contain the element, it is unchanged.
- * More formally, removes the first element e such that
- * o.equals(e) (if such an element exists).
- * Returns true if this deque contained the specified element
+ * More formally, removes the first element {@code e} such that
+ * {@code o.equals(e)} (if such an element exists).
+ * Returns {@code true} if this deque contained the specified element
* (or equivalently, if this deque changed as a result of the call).
*
* @param o element to be removed from this deque, if present
- * @return true if the deque contained the specified element
+ * @return {@code true} if the deque contained the specified element
*/
public boolean removeFirstOccurrence(Object o) {
if (o == null)
return false;
int mask = elements.length - 1;
int i = head;
- E x;
+ Object x;
while ( (x = elements[i]) != null) {
if (o.equals(x)) {
delete(i);
@@ -341,20 +380,20 @@ public class ArrayDeque extends Abstr
* Removes the last occurrence of the specified element in this
* deque (when traversing the deque from head to tail).
* If the deque does not contain the element, it is unchanged.
- * More formally, removes the last element e such that
- * o.equals(e) (if such an element exists).
- * Returns true if this deque contained the specified element
+ * More formally, removes the last element {@code e} such that
+ * {@code o.equals(e)} (if such an element exists).
+ * Returns {@code true} if this deque contained the specified element
* (or equivalently, if this deque changed as a result of the call).
*
* @param o element to be removed from this deque, if present
- * @return true if the deque contained the specified element
+ * @return {@code true} if the deque contained the specified element
*/
public boolean removeLastOccurrence(Object o) {
if (o == null)
return false;
int mask = elements.length - 1;
int i = (tail - 1) & mask;
- E x;
+ Object x;
while ( (x = elements[i]) != null) {
if (o.equals(x)) {
delete(i);
@@ -373,7 +412,7 @@ public class ArrayDeque extends Abstr
* This method is equivalent to {@link #addLast}.
*
* @param e the element to add
- * @return true (as specified by {@link Collection#add})
+ * @return {@code true} (as specified by {@link Collection#add})
* @throws NullPointerException if the specified element is null
*/
public boolean add(E e) {
@@ -387,7 +426,7 @@ public class ArrayDeque extends Abstr
* This method is equivalent to {@link #offerLast}.
*
* @param e the element to add
- * @return true (as specified by {@link Queue#offer})
+ * @return {@code true} (as specified by {@link Queue#offer})
* @throws NullPointerException if the specified element is null
*/
public boolean offer(E e) {
@@ -412,12 +451,12 @@ public class ArrayDeque extends Abstr
/**
* Retrieves and removes the head of the queue represented by this deque
* (in other words, the first element of this deque), or returns
- * null if this deque is empty.
+ * {@code null} if this deque is empty.
*
* This method is equivalent to {@link #pollFirst}.
*
* @return the head of the queue represented by this deque, or
- * null if this deque is empty
+ * {@code null} if this deque is empty
*/
public E poll() {
return pollFirst();
@@ -439,12 +478,12 @@ public class ArrayDeque extends Abstr
/**
* Retrieves, but does not remove, the head of the queue represented by
- * this deque, or returns null if this deque is empty.
+ * this deque, or returns {@code null} if this deque is empty.
*
* This method is equivalent to {@link #peekFirst}.
*
* @return the head of the queue represented by this deque, or
- * null if this deque is empty
+ * {@code null} if this deque is empty
*/
public E peek() {
return peekFirst();
@@ -479,6 +518,14 @@ public class ArrayDeque extends Abstr
return removeFirst();
}
+ private void checkInvariants() {
+ assert elements[tail] == null;
+ assert head == tail ? elements[head] == null :
+ (elements[head] != null &&
+ elements[(tail - 1) & (elements.length - 1)] != null);
+ assert elements[(head - 1) & (elements.length - 1)] == null;
+ }
+
/**
* Removes the element at the specified position in the elements array,
* adjusting head and tail as necessary. This can result in motion of
@@ -490,38 +537,42 @@ public class ArrayDeque extends Abstr
* @return true if elements moved backwards
*/
private boolean delete(int i) {
- int mask = elements.length - 1;
- int front = (i - head) & mask;
- int back = (tail - i) & mask;
-
- // Invariant: head <= i < tail mod circularity
- if (front >= ((tail - head) & mask))
- throw new ConcurrentModificationException();
-
- // Optimize for least element motion
- if (front < back) {
- if (head <= i) {
- System.arraycopy(elements, head, elements, head + 1, front);
- } else { // Wrap around
- elements[0] = elements[mask];
- System.arraycopy(elements, 0, elements, 1, i);
- System.arraycopy(elements, head, elements, head + 1, mask - head);
- }
- elements[head] = null;
- head = (head + 1) & mask;
+ checkInvariants();
+ final Object[] elements = this.elements;
+ final int mask = elements.length - 1;
+ final int h = head;
+ final int t = tail;
+ final int front = (i - h) & mask;
+ final int back = (t - i) & mask;
+
+ // Invariant: head <= i < tail mod circularity
+ if (front >= ((t - h) & mask))
+ throw new ConcurrentModificationException();
+
+ // Optimize for least element motion
+ if (front < back) {
+ if (h <= i) {
+ System.arraycopy(elements, h, elements, h + 1, front);
+ } else { // Wrap around
+ System.arraycopy(elements, 0, elements, 1, i);
+ elements[0] = elements[mask];
+ System.arraycopy(elements, h, elements, h + 1, mask - h);
+ }
+ elements[h] = null;
+ head = (h + 1) & mask;
return false;
- } else {
- int t = tail;
- tail = (tail - 1) & mask;
- if (i < t) { // Copy the null tail as well
- System.arraycopy(elements, i + 1, elements, i, back);
- } else { // Wrap around
- elements[mask] = elements[0];
- System.arraycopy(elements, i + 1, elements, i, mask - i);
- System.arraycopy(elements, 1, elements, 0, tail);
- }
+ } else {
+ if (i < t) { // Copy the null tail as well
+ System.arraycopy(elements, i + 1, elements, i, back);
+ tail = t - 1;
+ } else { // Wrap around
+ System.arraycopy(elements, i + 1, elements, i, mask - i);
+ elements[mask] = elements[0];
+ System.arraycopy(elements, 1, elements, 0, t);
+ tail = (t - 1) & mask;
+ }
return true;
- }
+ }
}
// *** Collection Methods ***
@@ -536,9 +587,9 @@ public class ArrayDeque extends Abstr
}
/**
- * Returns true if this deque contains no elements.
+ * Returns {@code true} if this deque contains no elements.
*
- * @return true if this deque contains no elements
+ * @return {@code true} if this deque contains no elements
*/
public boolean isEmpty() {
return head == tail;
@@ -583,12 +634,13 @@ public class ArrayDeque extends Abstr
}
public E next() {
- E result;
if (cursor == fence)
throw new NoSuchElementException();
+ @SuppressWarnings("unchecked")
+ E result = (E) elements[cursor];
// This check doesn't catch all possible comodifications,
// but does catch the ones that corrupt traversal
- if (tail != fence || (result = elements[cursor]) == null)
+ if (tail != fence || result == null)
throw new ConcurrentModificationException();
lastRet = cursor;
cursor = (cursor + 1) & (elements.length - 1);
@@ -598,66 +650,65 @@ public class ArrayDeque extends Abstr
public void remove() {
if (lastRet < 0)
throw new IllegalStateException();
- if (delete(lastRet)) // if left-shifted, undo increment in next()
+ if (delete(lastRet)) { // if left-shifted, undo increment in next()
cursor = (cursor - 1) & (elements.length - 1);
+ fence = tail;
+ }
lastRet = -1;
- fence = tail;
}
}
-
private class DescendingIterator implements Iterator {
/*
* This class is nearly a mirror-image of DeqIterator, using
- * (tail-1) instead of head for initial cursor, (head-1)
- * instead of tail for fence, and elements.length instead of -1
- * for sentinel. It shares the same structure, but not many
- * actual lines of code.
+ * tail instead of head for initial cursor, and head instead of
+ * tail for fence.
*/
- private int cursor = (tail - 1) & (elements.length - 1);
- private int fence = (head - 1) & (elements.length - 1);
- private int lastRet = elements.length;
+ private int cursor = tail;
+ private int fence = head;
+ private int lastRet = -1;
public boolean hasNext() {
return cursor != fence;
}
public E next() {
- E result;
if (cursor == fence)
throw new NoSuchElementException();
- if (((head - 1) & (elements.length - 1)) != fence ||
- (result = elements[cursor]) == null)
+ cursor = (cursor - 1) & (elements.length - 1);
+ @SuppressWarnings("unchecked")
+ E result = (E) elements[cursor];
+ if (head != fence || result == null)
throw new ConcurrentModificationException();
lastRet = cursor;
- cursor = (cursor - 1) & (elements.length - 1);
return result;
}
public void remove() {
- if (lastRet >= elements.length)
+ if (lastRet < 0)
throw new IllegalStateException();
- if (!delete(lastRet))
+ if (!delete(lastRet)) {
cursor = (cursor + 1) & (elements.length - 1);
- lastRet = elements.length;
- fence = (head - 1) & (elements.length - 1);
+ fence = head;
+ }
+ lastRet = -1;
}
}
/**
- * Returns true if this deque contains the specified element.
- * More formally, returns true if and only if this deque contains
- * at least one element e such that o.equals(e).
+ * Returns {@code true} if this deque contains the specified element.
+ * More formally, returns {@code true} if and only if this deque contains
+ * at least one element {@code e} such that {@code o.equals(e)}.
*
* @param o object to be checked for containment in this deque
- * @return true if this deque contains the specified element
+ * @return {@code true} if this deque contains the specified element
*/
public boolean contains(Object o) {
if (o == null)
return false;
int mask = elements.length - 1;
int i = head;
- E x;
+ Object x;
while ( (x = elements[i]) != null) {
if (o.equals(x))
return true;
@@ -669,15 +720,15 @@ public class ArrayDeque extends Abstr
/**
* Removes a single instance of the specified element from this deque.
* If the deque does not contain the element, it is unchanged.
- * More formally, removes the first element e such that
- * o.equals(e) (if such an element exists).
- * Returns true if this deque contained the specified element
+ * More formally, removes the first element {@code e} such that
+ * {@code o.equals(e)} (if such an element exists).
+ * Returns {@code true} if this deque contained the specified element
* (or equivalently, if this deque changed as a result of the call).
*
* This method is equivalent to {@link #removeFirstOccurrence}.
*
* @param o element to be removed from this deque, if present
- * @return true if this deque contained the specified element
+ * @return {@code true} if this deque contained the specified element
*/
public boolean remove(Object o) {
return removeFirstOccurrence(o);
@@ -715,7 +766,7 @@ public class ArrayDeque extends Abstr
* @return an array containing all of the elements in this deque
*/
public Object[] toArray() {
- return copyElements(new Object[size()]);
+ return copyElements(new Object[size()]);
}
/**
@@ -729,22 +780,21 @@ public class ArrayDeque extends Abstr
* If this deque fits in the specified array with room to spare
* (i.e., the array has more elements than this deque), the element in
* the array immediately following the end of the deque is set to
- * null.
+ * {@code null}.
*
*
Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
- *
Suppose x is a deque known to contain only strings.
+ *
Suppose {@code x} is a deque known to contain only strings.
* The following code can be used to dump the deque into a newly
- * allocated array of String:
+ * allocated array of {@code String}:
*
- *
- * String[] y = x.toArray(new String[0]);
+ * {@code String[] y = x.toArray(new String[0]);}
*
- * Note that toArray(new Object[0]) is identical in function to
- * toArray().
+ * Note that {@code toArray(new Object[0])} is identical in function to
+ * {@code toArray()}.
*
* @param a the array into which the elements of the deque are to
* be stored, if it is big enough; otherwise, a new array of the
@@ -755,12 +805,13 @@ public class ArrayDeque extends Abstr
* this deque
* @throws NullPointerException if the specified array is null
*/
+ @SuppressWarnings("unchecked")
public T[] toArray(T[] a) {
int size = size();
if (a.length < size)
a = (T[])java.lang.reflect.Array.newInstance(
a.getClass().getComponentType(), size);
- copyElements(a);
+ copyElements(a);
if (a.length > size)
a[size] = null;
return a;
@@ -775,30 +826,26 @@ public class ArrayDeque extends Abstr
*/
public ArrayDeque clone() {
try {
+ @SuppressWarnings("unchecked")
ArrayDeque result = (ArrayDeque) super.clone();
- // These two lines are currently faster than cloning the array:
- result.elements = (E[]) new Object[elements.length];
- System.arraycopy(elements, 0, result.elements, 0, elements.length);
+ result.elements = Arrays.copyOf(elements, elements.length);
return result;
-
} catch (CloneNotSupportedException e) {
throw new AssertionError();
}
}
- /**
- * Appease the serialization gods.
- */
private static final long serialVersionUID = 2340985798034038923L;
/**
- * Serialize this deque.
+ * Saves this deque to a stream (that is, serializes it).
*
- * @serialData The current size (int) of the deque,
+ * @serialData The current size ({@code int}) of the deque,
* followed by all of its elements (each an object reference) in
* first-to-last order.
*/
- private void writeObject(ObjectOutputStream s) throws IOException {
+ private void writeObject(java.io.ObjectOutputStream s)
+ throws java.io.IOException {
s.defaultWriteObject();
// Write out size
@@ -811,10 +858,10 @@ public class ArrayDeque extends Abstr
}
/**
- * Deserialize this deque.
+ * Reconstitutes this deque from a stream (that is, deserializes it).
*/
- private void readObject(ObjectInputStream s)
- throws IOException, ClassNotFoundException {
+ private void readObject(java.io.ObjectInputStream s)
+ throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
// Read in size and allocate array
@@ -825,7 +872,116 @@ public class ArrayDeque extends Abstr
// Read in all elements in the proper order.
for (int i = 0; i < size; i++)
- elements[i] = (E)s.readObject();
+ elements[i] = s.readObject();
+ }
+ public Stream stream() {
+ int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED;
+ return Streams.stream
+ (() -> new DeqSpliterator(this, head, tail), flags);
+ }
+ public Stream parallelStream() {
+ int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED;
+ return Streams.parallelStream
+ (() -> new DeqSpliterator(this, head, tail), flags);
}
+
+
+ static final class DeqSpliterator implements Spliterator, Iterator {
+ private final ArrayDeque deq;
+ private final Object[] array;
+ private final int fence; // initially tail
+ private int index; // current index, modified on traverse/split
+
+ /** Create new spliterator covering the given array and range */
+ DeqSpliterator(ArrayDeque deq, int origin, int fence) {
+ this.deq = deq; this.array = deq.elements;
+ this.index = origin; this.fence = fence;
+ }
+
+ public DeqSpliterator trySplit() {
+ int n = array.length;
+ int h = index, t = fence;
+ if (h != t && ((h + 1) & (n - 1)) != t) {
+ if (h > t)
+ t += n;
+ int m = ((h + t) >>> 1) & (n - 1);
+ return new DeqSpliterator(deq, h, index = m);
+ }
+ return null;
+ }
+
+ @SuppressWarnings("unchecked")
+ public void forEach(Block super E> block) {
+ if (block == null)
+ throw new NullPointerException();
+ Object[] a = array;
+ if (a != deq.elements)
+ throw new ConcurrentModificationException();
+ int m = a.length - 1, f = fence, i = index;
+ index = f;
+ while (i != f) {
+ Object e = a[i];
+ if (e == null)
+ throw new ConcurrentModificationException();
+ block.accept((E)e);
+ i = (i + 1) & m;
+ }
+ }
+
+ @SuppressWarnings("unchecked")
+ public boolean tryAdvance(Block super E> block) {
+ if (block == null)
+ throw new NullPointerException();
+ Object[] a = array;
+ if (a != deq.elements)
+ throw new ConcurrentModificationException();
+ int m = a.length - 1, i = index;
+ if (i != fence) {
+ Object e = a[i];
+ if (e == null)
+ throw new ConcurrentModificationException();
+ block.accept((E)e);
+ index = (i + 1) & m;
+ return true;
+ }
+ return false;
+ }
+
+ // Iterator support
+ public Iterator iterator() {
+ return this;
+ }
+
+ public boolean hasNext() {
+ return index >= 0 && index != fence;
+ }
+
+ @SuppressWarnings("unchecked")
+ public E next() {
+ if (index < 0 || index == fence)
+ throw new NoSuchElementException();
+ Object[] a = array;
+ if (a != deq.elements)
+ throw new ConcurrentModificationException();
+ Object e = a[index];
+ if (e == null)
+ throw new ConcurrentModificationException();
+ index = (index + 1) & (a.length - 1);
+ return (E) e;
+ }
+
+ public void remove() { throw new UnsupportedOperationException(); }
+
+ // Other spliterator methods
+ public long estimateSize() {
+ int n = fence - index;
+ if (n < 0)
+ n += array.length;
+ return (long)n;
+ }
+ public boolean hasExactSize() { return true; }
+ public boolean hasExactSplits() { return true; }
+ }
+
}