--- jsr166/src/main/java/util/ArrayDeque.java 2008/05/18 23:47:55 1.30
+++ jsr166/src/main/java/util/ArrayDeque.java 2013/02/17 23:36:16 1.47
@@ -1,10 +1,13 @@
/*
* 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.io.*;
+import java.io.Serializable;
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+import java.util.stream.Streams;
/**
* Resizable-array implementation of the {@link Deque} interface. Array
@@ -15,16 +18,16 @@ import java.io.*;
* {@link Stack} when used as a stack, and faster than {@link LinkedList}
* when used as a queue.
*
- *
Most ArrayDeque operations run in amortized constant time.
+ *
Most {@code ArrayDeque} operations run in amortized constant time.
* Exceptions include {@link #remove(Object) remove}, {@link
* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
* iterator.remove()}, and the bulk operations, all of which run in linear
* time.
*
- *
The iterators returned by this class's iterator method are
+ *
The iterators returned by this class's {@code iterator} method are
* fail-fast: If the deque is modified at any time after the iterator
- * is created, in any way except through the iterator's own remove
+ * is created, in any way except through the iterator's own {@code remove}
* method, the iterator will generally throw a {@link
* ConcurrentModificationException}. Thus, in the face of concurrent
* modification, the iterator fails quickly and cleanly, rather than risking
@@ -34,7 +37,7 @@ import java.io.*;
*
Note that the fail-fast behavior of an iterator cannot be guaranteed
* as it is, generally speaking, impossible to make any hard guarantees in the
* presence of unsynchronized concurrent modification. Fail-fast iterators
- * throw ConcurrentModificationException on a best-effort basis.
+ * throw {@code ConcurrentModificationException} on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: the fail-fast behavior of iterators
* should be used only to detect bugs.
@@ -64,20 +67,20 @@ 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.
@@ -88,7 +91,7 @@ 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
*/
@@ -108,11 +111,11 @@ 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() {
@@ -126,7 +129,7 @@ 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;
}
@@ -154,7 +157,7 @@ public class ArrayDeque extends Abstr
* sufficient to hold 16 elements.
*/
public ArrayDeque() {
- elements = (E[]) new Object[16];
+ elements = new Object[16];
}
/**
@@ -220,7 +223,7 @@ 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) {
@@ -232,7 +235,7 @@ 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) {
@@ -262,7 +265,9 @@ 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
@@ -272,7 +277,8 @@ 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;
@@ -284,48 +290,53 @@ 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);
@@ -340,20 +351,20 @@ 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);
@@ -372,7 +383,7 @@ 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) {
@@ -386,7 +397,7 @@ 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) {
@@ -411,12 +422,12 @@ 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();
@@ -438,12 +449,12 @@ 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();
@@ -498,7 +509,7 @@ public class ArrayDeque extends Abstr
*/
private boolean delete(int i) {
checkInvariants();
- final E[] elements = this.elements;
+ final Object[] elements = this.elements;
final int mask = elements.length - 1;
final int h = head;
final int t = tail;
@@ -547,9 +558,9 @@ 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;
@@ -596,7 +607,8 @@ public class ArrayDeque extends Abstr
public E next() {
if (cursor == fence)
throw new NoSuchElementException();
- E result = elements[cursor];
+ @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 == null)
@@ -635,7 +647,8 @@ public class ArrayDeque extends Abstr
if (cursor == fence)
throw new NoSuchElementException();
cursor = (cursor - 1) & (elements.length - 1);
- E result = elements[cursor];
+ @SuppressWarnings("unchecked")
+ E result = (E) elements[cursor];
if (head != fence || result == null)
throw new ConcurrentModificationException();
lastRet = cursor;
@@ -654,19 +667,19 @@ public class ArrayDeque extends Abstr
}
/**
- * 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;
@@ -678,15 +691,15 @@ 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}.
+ *
This method is equivalent to {@link #removeFirstOccurrence(Object)}.
*
* @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);
@@ -738,22 +751,21 @@ 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
@@ -764,6 +776,7 @@ 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)
@@ -784,28 +797,26 @@ public class ArrayDeque extends Abstr
*/
public ArrayDeque clone() {
try {
+ @SuppressWarnings("unchecked")
ArrayDeque result = (ArrayDeque) super.clone();
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
@@ -818,10 +829,10 @@ 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
@@ -832,6 +843,96 @@ 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();
+ }
+
+ Spliterator spliterator() {
+ return new DeqSpliterator(this, -1, -1);
+ }
+
+ public Stream stream() {
+ return Streams.stream(spliterator());
+ }
+
+ public Stream parallelStream() {
+ return Streams.parallelStream(spliterator());
+ }
+
+ static final class DeqSpliterator implements Spliterator {
+ private final ArrayDeque deq;
+ private int fence; // -1 until first use
+ 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.index = origin;
+ this.fence = fence;
+ }
+
+ private int getFence() { // force initialization
+ int t;
+ if ((t = fence) < 0) {
+ t = fence = deq.tail;
+ index = deq.head;
+ }
+ return t;
+ }
+
+ public DeqSpliterator trySplit() {
+ int t = getFence(), h = index, n = deq.elements.length;
+ 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;
+ }
+
+ public void forEach(Consumer super E> consumer) {
+ if (consumer == null)
+ throw new NullPointerException();
+ Object[] a = deq.elements;
+ int m = a.length - 1, f = getFence(), i = index;
+ index = f;
+ while (i != f) {
+ @SuppressWarnings("unchecked") E e = (E)a[i];
+ i = (i + 1) & m;
+ if (e == null)
+ throw new ConcurrentModificationException();
+ consumer.accept(e);
+ }
+ }
+
+ public boolean tryAdvance(Consumer super E> consumer) {
+ if (consumer == null)
+ throw new NullPointerException();
+ Object[] a = deq.elements;
+ int m = a.length - 1, f = getFence(), i = index;
+ if (i != fence) {
+ @SuppressWarnings("unchecked") E e = (E)a[i];
+ index = (i + 1) & m;
+ if (e == null)
+ throw new ConcurrentModificationException();
+ consumer.accept(e);
+ return true;
+ }
+ return false;
+ }
+
+ public long estimateSize() {
+ int n = getFence() - index;
+ if (n < 0)
+ n += deq.elements.length;
+ return (long) n;
+ }
+
+ @Override
+ public int characteristics() {
+ return Spliterator.ORDERED | Spliterator.SIZED |
+ Spliterator.NONNULL | Spliterator.SUBSIZED;
+ }
}
+
}