--- a/jdk/src/java.base/share/classes/java/util/ArrayDeque.java Tue Oct 13 16:35:22 2015 -0700
+++ b/jdk/src/java.base/share/classes/java/util/ArrayDeque.java Tue Oct 13 16:45:35 2015 -0700
@@ -47,16 +47,18 @@
* when used as a queue.
*
* <p>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.
+ * 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.
*
- * <p>The iterators returned by this class's {@code iterator} method are
- * <i>fail-fast</i>: If the deque is modified at any time after the iterator
- * is created, in any way except through the iterator's own {@code remove}
- * method, the iterator will generally throw a {@link
+ * <p>The iterators returned by this class's {@link #iterator() iterator}
+ * method are <em>fail-fast</em>: If the deque is modified at any time after
+ * the iterator 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
* arbitrary, non-deterministic behavior at an undetermined time in the
@@ -80,7 +82,7 @@
*
* @author Josh Bloch and Doug Lea
* @since 1.6
- * @param <E> the type of elements held in this collection
+ * @param <E> the type of elements held in this deque
*/
public class ArrayDeque<E> extends AbstractCollection<E>
implements Deque<E>, Cloneable, Serializable
@@ -136,8 +138,8 @@
initialCapacity |= (initialCapacity >>> 16);
initialCapacity++;
- if (initialCapacity < 0) // Too many elements, must back off
- initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
+ if (initialCapacity < 0) // Too many elements, must back off
+ initialCapacity >>>= 1; // Good luck allocating 2^30 elements
}
elements = new Object[initialCapacity];
}
@@ -163,24 +165,6 @@
}
/**
- * Copies the elements from our element array into the specified array,
- * in order (from first to last element in the deque). It is assumed
- * that the array is large enough to hold all elements in the deque.
- *
- * @return its argument
- */
- private <T> T[] copyElements(T[] a) {
- if (head < tail) {
- System.arraycopy(elements, head, a, 0, size());
- } else if (head > tail) {
- int headPortionLen = elements.length - head;
- System.arraycopy(elements, head, a, 0, headPortionLen);
- System.arraycopy(elements, 0, a, headPortionLen, tail);
- }
- return a;
- }
-
- /**
* Constructs an empty array deque with an initial capacity
* sufficient to hold 16 elements.
*/
@@ -292,25 +276,27 @@
}
public E pollFirst() {
- int h = head;
+ final Object[] elements = this.elements;
+ final int h = head;
@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
- head = (h + 1) & (elements.length - 1);
+ if (result != null) {
+ elements[h] = null; // Must null out slot
+ head = (h + 1) & (elements.length - 1);
+ }
return result;
}
public E pollLast() {
- int t = (tail - 1) & (elements.length - 1);
+ final Object[] elements = this.elements;
+ final int t = (tail - 1) & (elements.length - 1);
@SuppressWarnings("unchecked")
E result = (E) elements[t];
- if (result == null)
- return null;
- elements[t] = null;
- tail = t;
+ if (result != null) {
+ elements[t] = null;
+ tail = t;
+ }
return result;
}
@@ -360,17 +346,15 @@
* @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;
- Object x;
- while ( (x = elements[i]) != null) {
- if (o.equals(x)) {
- delete(i);
- return true;
+ if (o != null) {
+ int mask = elements.length - 1;
+ int i = head;
+ for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
+ if (o.equals(x)) {
+ delete(i);
+ return true;
+ }
}
- i = (i + 1) & mask;
}
return false;
}
@@ -388,17 +372,15 @@
* @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;
- Object x;
- while ( (x = elements[i]) != null) {
- if (o.equals(x)) {
- delete(i);
- return true;
+ if (o != null) {
+ int mask = elements.length - 1;
+ int i = (tail - 1) & mask;
+ for (Object x; (x = elements[i]) != null; i = (i - 1) & mask) {
+ if (o.equals(x)) {
+ delete(i);
+ return true;
+ }
}
- i = (i - 1) & mask;
}
return false;
}
@@ -535,7 +517,7 @@
*
* @return true if elements moved backwards
*/
- private boolean delete(int i) {
+ boolean delete(int i) {
checkInvariants();
final Object[] elements = this.elements;
final int mask = elements.length - 1;
@@ -671,12 +653,12 @@
}
}
+ /**
+ * This class is nearly a mirror-image of DeqIterator, using tail
+ * instead of head for initial cursor, and head instead of tail
+ * for fence.
+ */
private class DescendingIterator implements Iterator<E> {
- /*
- * This class is nearly a mirror-image of DeqIterator, using
- * tail instead of head for initial cursor, and head instead of
- * tail for fence.
- */
private int cursor = tail;
private int fence = head;
private int lastRet = -1;
@@ -717,15 +699,13 @@
* @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;
- Object x;
- while ( (x = elements[i]) != null) {
- if (o.equals(x))
- return true;
- i = (i + 1) & mask;
+ if (o != null) {
+ int mask = elements.length - 1;
+ int i = head;
+ for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
+ if (o.equals(x))
+ return true;
+ }
}
return false;
}
@@ -779,7 +759,14 @@
* @return an array containing all of the elements in this deque
*/
public Object[] toArray() {
- return copyElements(new Object[size()]);
+ final int head = this.head;
+ final int tail = this.tail;
+ boolean wrap = (tail < head);
+ int end = wrap ? tail + elements.length : tail;
+ Object[] a = Arrays.copyOfRange(elements, head, end);
+ if (wrap)
+ System.arraycopy(elements, 0, a, elements.length - head, tail);
+ return a;
}
/**
@@ -804,7 +791,7 @@
* The following code can be used to dump the deque into a newly
* allocated array of {@code String}:
*
- * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
+ * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
*
* Note that {@code toArray(new Object[0])} is identical in function to
* {@code toArray()}.
@@ -820,13 +807,22 @@
*/
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
- int size = size();
- if (a.length < size)
- a = (T[])java.lang.reflect.Array.newInstance(
- a.getClass().getComponentType(), size);
- copyElements(a);
- if (a.length > size)
- a[size] = null;
+ final int head = this.head;
+ final int tail = this.tail;
+ boolean wrap = (tail < head);
+ int size = (tail - head) + (wrap ? elements.length : 0);
+ int firstLeg = size - (wrap ? tail : 0);
+ int len = a.length;
+ if (size > len) {
+ a = (T[]) Arrays.copyOfRange(elements, head, head + size,
+ a.getClass());
+ } else {
+ System.arraycopy(elements, head, a, 0, firstLeg);
+ if (size < len)
+ a[size] = null;
+ }
+ if (wrap)
+ System.arraycopy(elements, 0, a, firstLeg, tail);
return a;
}
@@ -853,6 +849,8 @@
/**
* Saves this deque to a stream (that is, serializes it).
*
+ * @param s the stream
+ * @throws java.io.IOException if an I/O error occurs
* @serialData The current size ({@code int}) of the deque,
* followed by all of its elements (each an object reference) in
* first-to-last order.
@@ -872,6 +870,10 @@
/**
* Reconstitutes this deque from a stream (that is, deserializes it).
+ * @param s the stream
+ * @throws ClassNotFoundException if the class of a serialized object
+ * could not be found
+ * @throws java.io.IOException if an I/O error occurs
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
@@ -910,7 +912,7 @@
private int fence; // -1 until first use
private int index; // current index, modified on traverse/split
- /** Creates new spliterator covering the given array and range */
+ /** Creates new spliterator covering the given array and range. */
DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
this.deq = deq;
this.index = origin;
@@ -932,7 +934,7 @@
if (h > t)
t += n;
int m = ((h + t) >>> 1) & (n - 1);
- return new DeqSpliterator<>(deq, h, index = m);
+ return new DeqSpliterator<E>(deq, h, index = m);
}
return null;
}
@@ -957,7 +959,7 @@
throw new NullPointerException();
Object[] a = deq.elements;
int m = a.length - 1, f = getFence(), i = index;
- if (i != fence) {
+ if (i != f) {
@SuppressWarnings("unchecked") E e = (E)a[i];
index = (i + 1) & m;
if (e == null)