--- jsr166/src/main/java/util/ArrayDeque.java 2005/03/22 01:29:00 1.5
+++ jsr166/src/main/java/util/ArrayDeque.java 2016/10/30 20:10:34 1.102
@@ -1,10 +1,14 @@
/*
* 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.function.Predicate;
+import java.util.function.UnaryOperator;
/**
* Resizable-array implementation of the {@link Deque} interface. Array
@@ -15,135 +19,139 @@ 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.
- * 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.
+ *
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
- * 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 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 future.
+ *
The iterators returned by this class's {@link #iterator() 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
+ * {@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
+ * future.
*
*
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.
*
*
This class and its iterator implement all of the
- * optional methods of the {@link Collection} and {@link
- * Iterator} interfaces. This class is a member of the Java Collections
- * Framework.
+ * optional methods of the {@link Collection} and {@link
+ * Iterator} interfaces.
+ *
+ *
This class is a member of the
+ *
+ * Java Collections Framework.
*
* @author Josh Bloch and Doug Lea
+ * @param the type of elements held in this deque
* @since 1.6
- * @param the type of elements held in this collection
*/
public class ArrayDeque extends AbstractCollection
implements Deque, Cloneable, Serializable
{
/**
* The array in which the elements of the deque are stored.
- * The capacity of the deque is the length of this array, which is
- * always a power of two. The array is never allowed to become
- * full, except transiently within an addX method where it is
- * resized (see doubleCapacity) immediately upon becoming full,
- * thus avoiding head and tail wrapping around to equal each
- * other. We also guarantee that all array cells not holding
- * deque elements are always null.
+ * We guarantee that all array cells not holding deque elements
+ * are always null.
*/
- private transient E[] elements;
+ transient Object[] elements;
/**
* 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;
-
- /**
- * 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;
-
- /**
- * The minimum capacity that we'll use for a newly created deque.
- * Must be a power of 2.
+ * arbitrary number 0 <= head < elements.length if the deque is empty.
*/
- private static final int MIN_INITIAL_CAPACITY = 8;
+ transient int head;
- // ****** Array allocation and resizing utilities ******
+ /** Number of elements in this collection. */
+ transient int size;
/**
- * Allocate empty array to hold the given number of elements.
- *
- * @param numElements the number of elements to hold.
- */
- private void allocateElements(int numElements) {
- int initialCapacity = MIN_INITIAL_CAPACITY;
- // Find the best power of two to hold elements.
- // Tests "<=" because arrays aren't kept full.
- if (numElements >= initialCapacity) {
- initialCapacity = numElements;
- initialCapacity |= (initialCapacity >>> 1);
- initialCapacity |= (initialCapacity >>> 2);
- initialCapacity |= (initialCapacity >>> 4);
- initialCapacity |= (initialCapacity >>> 8);
- initialCapacity |= (initialCapacity >>> 16);
- initialCapacity++;
+ * The maximum size of array to allocate.
+ * Some VMs reserve some header words in an array.
+ * Attempts to allocate larger arrays may result in
+ * OutOfMemoryError: Requested array size exceeds VM limit
+ */
+ private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
+
+ /**
+ * Increases the capacity of this deque by at least the given amount.
+ *
+ * @param needed the required minimum extra capacity; must be positive
+ */
+ private void grow(int needed) {
+ // overflow-conscious code
+ // checkInvariants();
+ final int oldCapacity = elements.length;
+ int newCapacity;
+ // Double size if small; else grow by 50%
+ int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
+ if (jump < needed
+ || (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
+ newCapacity = newCapacity(needed, jump);
+ elements = Arrays.copyOf(elements, newCapacity);
+ if (oldCapacity - head < size) {
+ // wrap around; slide first leg forward to end of array
+ int newSpace = newCapacity - oldCapacity;
+ System.arraycopy(elements, head,
+ elements, head + newSpace,
+ oldCapacity - head);
+ Arrays.fill(elements, head, head + newSpace, null);
+ head += newSpace;
+ }
+ // checkInvariants();
+ }
- if (initialCapacity < 0) // Too many elements, must back off
- initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
+ /** Capacity calculation for edge conditions, especially overflow. */
+ private int newCapacity(int needed, int jump) {
+ final int oldCapacity = elements.length, minCapacity;
+ if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
+ if (minCapacity < 0)
+ throw new IllegalStateException("Sorry, deque too big");
+ return Integer.MAX_VALUE;
}
- elements = (E[]) new Object[initialCapacity];
+ if (needed > jump)
+ return minCapacity;
+ return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
+ ? oldCapacity + jump
+ : MAX_ARRAY_SIZE;
}
/**
- * Double the capacity of this deque. Call only when full, i.e.,
- * when head and tail have wrapped around to become equal.
+ * Increases the internal storage of this collection, if necessary,
+ * to ensure that it can hold at least the given number of elements.
+ *
+ * @param minCapacity the desired minimum capacity
+ * @since TBD
*/
- private void doubleCapacity() {
- assert head == tail;
- int p = head;
- int n = elements.length;
- int r = n - p; // number of elements to the right of p
- int newCapacity = n << 1;
- if (newCapacity < 0)
- throw new IllegalStateException("Sorry, deque too big");
- Object[] a = new Object[newCapacity];
- System.arraycopy(elements, p, a, 0, r);
- System.arraycopy(elements, 0, a, r, p);
- elements = (E[])a;
- head = 0;
- tail = n;
+ /* public */ void ensureCapacity(int minCapacity) {
+ if (minCapacity > elements.length)
+ grow(minCapacity - elements.length);
+ // checkInvariants();
}
/**
- * Copy 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.
+ * Minimizes the internal storage of this collection.
*
- * @return its argument
+ * @since TBD
*/
- private 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);
+ /* public */ void trimToSize() {
+ if (size < elements.length) {
+ elements = toArray();
+ head = 0;
}
- return a;
+ // checkInvariants();
}
/**
@@ -151,17 +159,17 @@ public class ArrayDeque extends Abstr
* sufficient to hold 16 elements.
*/
public ArrayDeque() {
- elements = (E[]) new Object[16];
+ elements = new Object[16];
}
/**
* Constructs an empty array deque with an initial capacity
* sufficient to hold the specified number of elements.
*
- * @param numElements lower bound on initial capacity of the deque
+ * @param numElements lower bound on initial capacity of the deque
*/
public ArrayDeque(int numElements) {
- allocateElements(numElements);
+ elements = new Object[numElements];
}
/**
@@ -175,84 +183,148 @@ public class ArrayDeque extends Abstr
* @throws NullPointerException if the specified collection is null
*/
public ArrayDeque(Collection c) {
- allocateElements(c.size());
- addAll(c);
+ Object[] es = c.toArray();
+ // defend against c.toArray (incorrectly) not returning Object[]
+ // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
+ if (es.getClass() != Object[].class)
+ es = Arrays.copyOf(es, es.length, Object[].class);
+ for (Object obj : es)
+ Objects.requireNonNull(obj);
+ this.elements = es;
+ this.size = es.length;
}
- // The main insertion and extraction methods are addFirst,
- // addLast, pollFirst, pollLast. The other methods are defined in
- // terms of these.
+ /**
+ * Increments i, mod modulus.
+ * Precondition and postcondition: 0 <= i < modulus.
+ */
+ static final int inc(int i, int modulus) {
+ if (++i >= modulus) i = 0;
+ return i;
+ }
/**
- * Inserts the specified element at the front of this deque.
- *
- * @param e the element to insert
- * @throws NullPointerException if e is null
+ * Decrements i, mod modulus.
+ * Precondition and postcondition: 0 <= i < modulus.
*/
- public void addFirst(E e) {
- if (e == null)
- throw new NullPointerException();
- elements[head = (head - 1) & (elements.length - 1)] = e;
- if (head == tail)
- doubleCapacity();
+ static final int dec(int i, int modulus) {
+ if (--i < 0) i = modulus - 1;
+ return i;
}
/**
- * Inserts the specified element to the end of this deque.
- * This method is equivalent to {@link Collection#add} and
- * {@link #push}.
- *
- * @param e the element to insert
- * @throws NullPointerException if e is null
+ * Adds i and j, mod modulus.
+ * Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
*/
- public void addLast(E e) {
+ static final int add(int i, int j, int modulus) {
+ if ((i += j) - modulus >= 0) i -= modulus;
+ return i;
+ }
+
+ /**
+ * Returns the array index of the last element.
+ * May return invalid index -1 if there are no elements.
+ */
+ final int tail() {
+ return add(head, size - 1, elements.length);
+ }
+
+ /**
+ * Returns element at array index i.
+ */
+ @SuppressWarnings("unchecked")
+ private E elementAt(int i) {
+ return (E) elements[i];
+ }
+
+ /**
+ * A version of elementAt that checks for null elements.
+ * This check doesn't catch all possible comodifications,
+ * but does catch ones that corrupt traversal. It's a little
+ * surprising that javac allows this abuse of generics.
+ */
+ static final E nonNullElementAt(Object[] es, int i) {
+ @SuppressWarnings("unchecked") E e = (E) es[i];
if (e == null)
- throw new NullPointerException();
- elements[tail] = e;
- if ( (tail = (tail + 1) & (elements.length - 1)) == head)
- doubleCapacity();
+ throw new ConcurrentModificationException();
+ return e;
}
+ // The main insertion and extraction methods are addFirst,
+ // addLast, pollFirst, pollLast. The other methods are defined in
+ // terms of these.
+
/**
- * Retrieves and removes the first element of this deque, or
- * null if this deque is empty.
+ * Inserts the specified element at the front of this deque.
*
- * @return the first element of this deque, or null if
- * this deque is empty
+ * @param e the element to add
+ * @throws NullPointerException if the specified element is null
*/
- public E pollFirst() {
- int h = head;
- E result = 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);
- return result;
+ public void addFirst(E e) {
+ // checkInvariants();
+ Objects.requireNonNull(e);
+ Object[] es;
+ int capacity, h;
+ final int s;
+ if ((s = size) == (capacity = (es = elements).length)) {
+ grow(1);
+ capacity = (es = elements).length;
+ }
+ if ((h = head - 1) < 0) h = capacity - 1;
+ es[head = h] = e;
+ size = s + 1;
+ // checkInvariants();
}
/**
- * Retrieves and removes the last element of this deque, or
- * null if this deque is empty.
+ * Inserts the specified element at the end of this deque.
*
- * @return the last element of this deque, or null if
- * this deque is empty
+ * This method is equivalent to {@link #add}.
+ *
+ * @param e the element to add
+ * @throws NullPointerException if the specified element is null
*/
- public E pollLast() {
- int t = (tail - 1) & (elements.length - 1);
- E result = elements[t];
- if (result == null)
- return null;
- elements[t] = null;
- tail = t;
- return result;
+ public void addLast(E e) {
+ // checkInvariants();
+ Objects.requireNonNull(e);
+ Object[] es;
+ int capacity;
+ final int s;
+ if ((s = size) == (capacity = (es = elements).length)) {
+ grow(1);
+ capacity = (es = elements).length;
+ }
+ es[add(head, s, capacity)] = e;
+ size = s + 1;
+ // checkInvariants();
+ }
+
+ /**
+ * Adds all of the elements in the specified collection at the end
+ * of this deque, as if by calling {@link #addLast} on each one,
+ * in the order that they are returned by the collection's
+ * iterator.
+ *
+ * @param c the elements to be inserted into this deque
+ * @return {@code true} if this deque changed as a result of the call
+ * @throws NullPointerException if the specified collection or any
+ * of its elements are null
+ */
+ public boolean addAll(Collection c) {
+ final int s = size, needed = c.size() - (elements.length - s);
+ if (needed > 0)
+ grow(needed);
+ c.forEach((e) -> addLast(e));
+ // checkInvariants();
+ return size > s;
}
/**
* Inserts the specified element at the front of this deque.
*
- * @param e the element to insert
- * @return true (as per the spec for {@link Deque#offerFirst})
- * @throws NullPointerException if e is null
+ * @param e the element to add
+ * @return {@code true} (as specified by {@link Deque#offerFirst})
+ * @throws NullPointerException if the specified element is null
*/
public boolean offerFirst(E e) {
addFirst(e);
@@ -260,11 +332,11 @@ public class ArrayDeque extends Abstr
}
/**
- * Inserts the specified element to the end of this deque.
+ * Inserts the specified element at the end of this deque.
*
- * @param e the element to insert
- * @return true (as per the spec for {@link Deque#offerLast})
- * @throws NullPointerException if e is null
+ * @param e the element to add
+ * @return {@code true} (as specified by {@link Deque#offerLast})
+ * @throws NullPointerException if the specified element is null
*/
public boolean offerLast(E e) {
addLast(e);
@@ -272,135 +344,144 @@ public class ArrayDeque extends Abstr
}
/**
- * Retrieves and removes the first element of this deque. This method
- * differs from the pollFirst method in that it throws an
- * exception if this deque is empty.
- *
- * @return the first element of this deque
- * @throws NoSuchElementException if this deque is empty
+ * @throws NoSuchElementException {@inheritDoc}
*/
public E removeFirst() {
- E x = pollFirst();
- if (x == null)
+ // checkInvariants();
+ E e = pollFirst();
+ if (e == null)
throw new NoSuchElementException();
- return x;
+ return e;
}
/**
- * Retrieves and removes the last element of this deque. This method
- * differs from the pollLast method in that it throws an
- * exception if this deque is empty.
- *
- * @return the last element of this deque
- * @throws NoSuchElementException if this deque is empty
+ * @throws NoSuchElementException {@inheritDoc}
*/
public E removeLast() {
- E x = pollLast();
- if (x == null)
+ // checkInvariants();
+ E e = pollLast();
+ if (e == null)
throw new NoSuchElementException();
- return x;
+ return e;
}
- /**
- * Retrieves, but does not remove, the first element of this deque,
- * returning null if this deque is empty.
- *
- * @return the first element of this deque, or null if
- * this deque is empty
- */
- public E peekFirst() {
- return elements[head]; // elements[head] is null if deque empty
+ public E pollFirst() {
+ // checkInvariants();
+ int s, h;
+ if ((s = size) <= 0)
+ return null;
+ final Object[] es = elements;
+ @SuppressWarnings("unchecked") E e = (E) es[h = head];
+ es[h] = null;
+ if (++h >= es.length) h = 0;
+ head = h;
+ size = s - 1;
+ return e;
}
- /**
- * Retrieves, but does not remove, the last element of this deque,
- * returning null if this deque is empty.
- *
- * @return the last element of this deque, or null if this deque
- * is empty
- */
- public E peekLast() {
- return elements[(tail - 1) & (elements.length - 1)];
+ public E pollLast() {
+ // checkInvariants();
+ final int s, tail;
+ if ((s = size) <= 0)
+ return null;
+ final Object[] es = elements;
+ @SuppressWarnings("unchecked")
+ E e = (E) es[tail = add(head, s - 1, es.length)];
+ es[tail] = null;
+ size = s - 1;
+ return e;
}
/**
- * Retrieves, but does not remove, the first element of this
- * deque. This method differs from the peekFirst method only
- * in that it throws an exception if this deque is empty.
- *
- * @return the first element of this deque
- * @throws NoSuchElementException if this deque is empty
+ * @throws NoSuchElementException {@inheritDoc}
*/
public E getFirst() {
- E x = elements[head];
- if (x == null)
- throw new NoSuchElementException();
- return x;
+ // checkInvariants();
+ if (size <= 0) throw new NoSuchElementException();
+ return elementAt(head);
}
/**
- * Retrieves, but does not remove, the last element of this
- * deque. This method differs from the peekLast method only
- * in that it throws an exception if this deque is empty.
- *
- * @return the last element of this deque
- * @throws NoSuchElementException if this deque is empty
+ * @throws NoSuchElementException {@inheritDoc}
*/
+ @SuppressWarnings("unchecked")
public E getLast() {
- E x = elements[(tail - 1) & (elements.length - 1)];
- if (x == null)
- throw new NoSuchElementException();
- return x;
+ // checkInvariants();
+ final int s;
+ if ((s = size) <= 0) throw new NoSuchElementException();
+ final Object[] es = elements;
+ return (E) es[add(head, s - 1, es.length)];
+ }
+
+ public E peekFirst() {
+ // checkInvariants();
+ return (size <= 0) ? null : elementAt(head);
+ }
+
+ @SuppressWarnings("unchecked")
+ public E peekLast() {
+ // checkInvariants();
+ final int s;
+ if ((s = size) <= 0) return null;
+ final Object[] es = elements;
+ return (E) es[add(head, s - 1, es.length)];
}
/**
* Removes the first occurrence of the specified element in this
- * deque (when traversing the deque from head to tail). More
- * formally, removes the first element e such that (o==null ?
- * e==null : o.equals(e)). If the deque does not contain the
- * element, it is unchanged.
+ * 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 {@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;
- while ( (x = elements[i]) != null) {
- if (o.equals(x)) {
- delete(i);
- return true;
+ if (o != null) {
+ final Object[] es = elements;
+ int i, end, to, todo;
+ todo = (end = (i = head) + size)
+ - (to = (es.length - end >= 0) ? end : es.length);
+ for (;; to = todo, i = 0, todo = 0) {
+ for (; i < to; i++)
+ if (o.equals(es[i])) {
+ delete(i);
+ return true;
+ }
+ if (todo == 0) break;
}
- i = (i + 1) & mask;
}
return false;
}
/**
* Removes the last occurrence of the specified element in this
- * deque (when traversing the deque from head to tail). More
- * formally, removes the last element e such that (o==null ?
- * e==null : o.equals(e)). If the deque
- * does not contain the element, it is unchanged.
+ * 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 {@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;
- while ( (x = elements[i]) != null) {
- if (o.equals(x)) {
- delete(i);
- return true;
+ if (o != null) {
+ final Object[] es = elements;
+ int i, to, end, todo;
+ todo = (to = ((end = (i = tail()) - size) >= -1) ? end : -1) - end;
+ for (;; to = (i = es.length - 1) - todo, todo = 0) {
+ for (; i > to; i--)
+ if (o.equals(es[i])) {
+ delete(i);
+ return true;
+ }
+ if (todo == 0) break;
}
- i = (i - 1) & mask;
}
return false;
}
@@ -408,26 +489,13 @@ public class ArrayDeque extends Abstr
// *** Queue methods ***
/**
- * Inserts the specified element to the end of this deque.
- *
- * This method is equivalent to {@link #offerLast}.
- *
- * @param e the element to insert
- * @return true (as per the spec for {@link Queue#offer})
- * @throws NullPointerException if e is null
- */
- public boolean offer(E e) {
- return offerLast(e);
- }
-
- /**
- * Inserts the specified element to the end of this deque.
+ * Inserts the specified element at the end of this deque.
*
*
This method is equivalent to {@link #addLast}.
*
- * @param e the element to insert
- * @return true (as per the spec for {@link Collection#add})
- * @throws NullPointerException if e is null
+ * @param e the element to add
+ * @return {@code true} (as specified by {@link Collection#add})
+ * @throws NullPointerException if the specified element is null
*/
public boolean add(E e) {
addLast(e);
@@ -435,61 +503,74 @@ public class ArrayDeque extends Abstr
}
/**
- * Retrieves and removes the head of the queue represented by
- * this deque, or null if this deque is empty. In other words,
- * retrieves and removes the first element of this deque, or null
- * if this deque is empty.
+ * Inserts the specified element at the end of this deque.
*
- * This method is equivalent to {@link #pollFirst}.
+ *
This method is equivalent to {@link #offerLast}.
*
- * @return the first element of this deque, or null if
- * this deque is empty
+ * @param e the element to add
+ * @return {@code true} (as specified by {@link Queue#offer})
+ * @throws NullPointerException if the specified element is null
*/
- public E poll() {
- return pollFirst();
+ public boolean offer(E e) {
+ return offerLast(e);
}
/**
* Retrieves and removes the head of the queue represented by this deque.
- * This method differs from the poll method in that it throws an
+ *
+ * This method differs from {@link #poll poll} only in that it throws an
* exception if this deque is empty.
*
*
This method is equivalent to {@link #removeFirst}.
*
* @return the head of the queue represented by this deque
- * @throws NoSuchElementException if this deque is empty
+ * @throws NoSuchElementException {@inheritDoc}
*/
public E remove() {
return removeFirst();
}
/**
- * Retrieves, but does not remove, the head of the queue represented by
- * this deque, returning null if this deque is empty.
+ * Retrieves and removes the head of the queue represented by this deque
+ * (in other words, the first element of this deque), or returns
+ * {@code null} if this deque is empty.
*
- *
This method is equivalent to {@link #peekFirst}
+ *
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 peek() {
- return peekFirst();
+ public E poll() {
+ return pollFirst();
}
/**
* Retrieves, but does not remove, the head of the queue represented by
- * this deque. This method differs from the peek method only in
+ * this deque. This method differs from {@link #peek peek} only in
* that it throws an exception if this deque is empty.
*
- *
This method is equivalent to {@link #getFirst}
+ *
This method is equivalent to {@link #getFirst}.
*
* @return the head of the queue represented by this deque
- * @throws NoSuchElementException if this deque is empty
+ * @throws NoSuchElementException {@inheritDoc}
*/
public E element() {
return getFirst();
}
+ /**
+ * Retrieves, but does not remove, the head of the queue represented by
+ * 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
+ * {@code null} if this deque is empty
+ */
+ public E peek() {
+ return peekFirst();
+ }
+
// *** Stack methods ***
/**
@@ -499,7 +580,7 @@ public class ArrayDeque extends Abstr
* This method is equivalent to {@link #addFirst}.
*
* @param e the element to push
- * @throws NullPointerException if e is null
+ * @throws NullPointerException if the specified element is null
*/
public void push(E e) {
addFirst(e);
@@ -512,38 +593,61 @@ public class ArrayDeque extends Abstr
* This method is equivalent to {@link #removeFirst()}.
*
* @return the element at the front of this deque (which is the top
- * of the stack represented by this deque)
- * @throws NoSuchElementException if this deque is empty
+ * of the stack represented by this deque)
+ * @throws NoSuchElementException {@inheritDoc}
*/
public E pop() {
return removeFirst();
}
/**
- * Remove the element at the specified position in the elements array,
- * adjusting head, tail, and size as necessary. This can result in
- * motion of elements backwards or forwards in the array.
+ * Removes the element at the specified position in the elements array.
+ * This can result in forward or backwards motion of array elements.
+ * We optimize for least element motion.
*
*
This method is called delete rather than remove to emphasize
- * that its semantics differ from those of List.remove(int).
+ * that its semantics differ from those of {@link List#remove(int)}.
*
* @return true if elements moved backwards
*/
- private boolean delete(int i) {
- // Case 1: Deque doesn't wrap
- // Case 2: Deque does wrap and removed element is in the head portion
- if ((head < tail || tail == 0) || i >= head) {
- System.arraycopy(elements, head, elements, head + 1, i - head);
- elements[head] = null;
- head = (head + 1) & (elements.length - 1);
+ boolean delete(int i) {
+ // checkInvariants();
+ final Object[] es = elements;
+ final int capacity = es.length;
+ final int h = head;
+ int front; // number of elements before to-be-deleted elt
+ if ((front = i - h) < 0) front += capacity;
+ final int back = size - front - 1; // number of elements after
+ if (front < back) {
+ // move front elements forwards
+ if (h <= i) {
+ System.arraycopy(es, h, es, h + 1, front);
+ } else { // Wrap around
+ System.arraycopy(es, 0, es, 1, i);
+ es[0] = es[capacity - 1];
+ System.arraycopy(es, h, es, h + 1, front - (i + 1));
+ }
+ es[h] = null;
+ if ((head = (h + 1)) >= capacity) head = 0;
+ size--;
+ // checkInvariants();
return false;
+ } else {
+ // move back elements backwards
+ int tail = tail();
+ if (i <= tail) {
+ System.arraycopy(es, i + 1, es, i, back);
+ } else { // Wrap around
+ int firstLeg = capacity - (i + 1);
+ System.arraycopy(es, i + 1, es, i, firstLeg);
+ es[capacity - 1] = es[0];
+ System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
+ }
+ es[tail] = null;
+ size--;
+ // checkInvariants();
+ return true;
}
-
- // Case 3: Deque wraps and removed element is in the tail portion
- tail--;
- System.arraycopy(elements, i + 1, elements, i, tail - i);
- elements[tail] = null;
- return true;
}
// *** Collection Methods ***
@@ -554,16 +658,16 @@ public class ArrayDeque extends Abstr
* @return the number of elements in this deque
*/
public int size() {
- return (tail - head) & (elements.length - 1);
+ return size;
}
/**
- * Returns true if this collection contains no elements.
+ * Returns {@code true} if this deque contains no elements.
*
- * @return true if this collection contains no elements.
+ * @return {@code true} if this deque contains no elements
*/
public boolean isEmpty() {
- return head == tail;
+ return size == 0;
}
/**
@@ -572,144 +676,449 @@ public class ArrayDeque extends Abstr
* order that elements would be dequeued (via successive calls to
* {@link #remove} or popped (via successive calls to {@link #pop}).
*
- * @return an Iterator over the elements in this deque
+ * @return an iterator over the elements in this deque
*/
public Iterator iterator() {
return new DeqIterator();
}
+ public Iterator descendingIterator() {
+ return new DescendingIterator();
+ }
+
private class DeqIterator implements Iterator {
- /**
- * Index of element to be returned by subsequent call to next.
- */
- private int cursor = head;
+ /** Index of element to be returned by subsequent call to next. */
+ int cursor;
- /**
- * Tail recorded at construction (also in remove), to stop
- * iterator and also to check for comodification.
- */
- private int fence = tail;
+ /** Number of elements yet to be returned. */
+ int remaining = size;
/**
* Index of element returned by most recent call to next.
* Reset to -1 if element is deleted by a call to remove.
*/
- private int lastRet = -1;
+ int lastRet = -1;
+
+ DeqIterator() { cursor = head; }
- public boolean hasNext() {
- return cursor != fence;
+ public final boolean hasNext() {
+ return remaining > 0;
}
public E next() {
- E result;
- if (cursor == fence)
+ if (remaining <= 0)
throw new NoSuchElementException();
- // This check doesn't catch all possible comodifications,
- // but does catch the ones that corrupt traversal
- if (tail != fence || (result = elements[cursor]) == null)
- throw new ConcurrentModificationException();
+ final Object[] es = elements;
+ E e = nonNullElementAt(es, cursor);
lastRet = cursor;
- cursor = (cursor + 1) & (elements.length - 1);
- return result;
+ if (++cursor >= es.length) cursor = 0;
+ remaining--;
+ return e;
+ }
+
+ void postDelete(boolean leftShifted) {
+ if (leftShifted)
+ if (--cursor < 0) cursor = elements.length - 1;
}
- public void remove() {
+ public final void remove() {
if (lastRet < 0)
throw new IllegalStateException();
- if (delete(lastRet))
- cursor--;
+ postDelete(delete(lastRet));
lastRet = -1;
- fence = tail;
+ }
+
+ public void forEachRemaining(Consumer action) {
+ Objects.requireNonNull(action);
+ final int k;
+ if ((k = remaining) > 0) {
+ remaining = 0;
+ ArrayDeque.forEachRemaining(action, elements, cursor, k);
+ if ((lastRet = cursor + k - 1) >= elements.length)
+ lastRet -= elements.length;
+ }
+ }
+ }
+
+ private class DescendingIterator extends DeqIterator {
+ DescendingIterator() { cursor = tail(); }
+
+ public final E next() {
+ if (remaining <= 0)
+ throw new NoSuchElementException();
+ final Object[] es = elements;
+ E e = nonNullElementAt(es, cursor);
+ lastRet = cursor;
+ if (--cursor < 0) cursor = es.length - 1;
+ remaining--;
+ return e;
+ }
+
+ void postDelete(boolean leftShifted) {
+ if (!leftShifted)
+ if (++cursor >= elements.length) cursor = 0;
+ }
+
+ public final void forEachRemaining(Consumer action) {
+ Objects.requireNonNull(action);
+ final int k;
+ if ((k = remaining) > 0) {
+ remaining = 0;
+ final Object[] es = elements;
+ int i, end, to, todo;
+ todo = (to = ((end = (i = cursor) - k) >= -1) ? end : -1) - end;
+ for (;; to = (i = es.length - 1) - todo, todo = 0) {
+ for (; i > to; i--)
+ action.accept(nonNullElementAt(es, i));
+ if (todo == 0) break;
+ }
+ if ((lastRet = cursor - (k - 1)) < 0)
+ lastRet += es.length;
+ }
}
}
/**
- * 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
- * e.equals(o).
+ * Creates a late-binding
+ * and fail-fast {@link Spliterator} over the elements in this
+ * deque.
+ *
+ * The {@code Spliterator} reports {@link Spliterator#SIZED},
+ * {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
+ * {@link Spliterator#NONNULL}. Overriding implementations should document
+ * the reporting of additional characteristic values.
+ *
+ * @return a {@code Spliterator} over the elements in this deque
+ * @since 1.8
+ */
+ public Spliterator spliterator() {
+ return new ArrayDequeSpliterator();
+ }
+
+ final class ArrayDequeSpliterator implements Spliterator {
+ private int cursor;
+ private int remaining; // -1 until late-binding first use
+
+ /** Constructs late-binding spliterator over all elements. */
+ ArrayDequeSpliterator() {
+ this.remaining = -1;
+ }
+
+ /** Constructs spliterator over the given slice. */
+ ArrayDequeSpliterator(int cursor, int count) {
+ this.cursor = cursor;
+ this.remaining = count;
+ }
+
+ /** Ensures late-binding initialization; then returns remaining. */
+ private int remaining() {
+ if (remaining < 0) {
+ cursor = head;
+ remaining = size;
+ }
+ return remaining;
+ }
+
+ public ArrayDequeSpliterator trySplit() {
+ final int mid;
+ if ((mid = remaining() >> 1) > 0) {
+ int oldCursor = cursor;
+ cursor = add(cursor, mid, elements.length);
+ remaining -= mid;
+ return new ArrayDequeSpliterator(oldCursor, mid);
+ }
+ return null;
+ }
+
+ public void forEachRemaining(Consumer action) {
+ Objects.requireNonNull(action);
+ final int k = remaining(); // side effect!
+ remaining = 0;
+ ArrayDeque.forEachRemaining(action, elements, cursor, k);
+ }
+
+ public boolean tryAdvance(Consumer action) {
+ Objects.requireNonNull(action);
+ final int k;
+ if ((k = remaining()) <= 0)
+ return false;
+ action.accept(nonNullElementAt(elements, cursor));
+ if (++cursor >= elements.length) cursor = 0;
+ remaining = k - 1;
+ return true;
+ }
+
+ public long estimateSize() {
+ return remaining();
+ }
+
+ public int characteristics() {
+ return Spliterator.NONNULL
+ | Spliterator.ORDERED
+ | Spliterator.SIZED
+ | Spliterator.SUBSIZED;
+ }
+ }
+
+ @SuppressWarnings("unchecked")
+ public void forEach(Consumer action) {
+ Objects.requireNonNull(action);
+ final Object[] es = elements;
+ int i, end, to, todo;
+ todo = (end = (i = head) + size)
+ - (to = (es.length - end >= 0) ? end : es.length);
+ for (;; to = todo, i = 0, todo = 0) {
+ for (; i < to; i++)
+ action.accept((E) es[i]);
+ if (todo == 0) break;
+ }
+ // checkInvariants();
+ }
+
+ /**
+ * Calls action on remaining elements, starting at index i and
+ * traversing in ascending order. A variant of forEach that also
+ * checks for concurrent modification, for use in iterators.
+ */
+ static void forEachRemaining(
+ Consumer action, Object[] es, int i, int remaining) {
+ int end, to, todo;
+ todo = (end = i + remaining)
+ - (to = (es.length - end >= 0) ? end : es.length);
+ for (;; to = todo, i = 0, todo = 0) {
+ for (; i < to; i++)
+ action.accept(nonNullElementAt(es, i));
+ if (todo == 0) break;
+ }
+ }
+
+ /**
+ * Replaces each element of this deque with the result of applying the
+ * operator to that element, as specified by {@link List#replaceAll}.
+ *
+ * @param operator the operator to apply to each element
+ * @since TBD
+ */
+ @SuppressWarnings("unchecked")
+ /* public */ void replaceAll(UnaryOperator operator) {
+ Objects.requireNonNull(operator);
+ final Object[] es = elements;
+ int i, end, to, todo;
+ todo = (end = (i = head) + size)
+ - (to = (es.length - end >= 0) ? end : es.length);
+ for (;; to = todo, i = 0, todo = 0) {
+ for (; i < to; i++)
+ es[i] = operator.apply((E) es[i]);
+ if (todo == 0) break;
+ }
+ // checkInvariants();
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean removeIf(Predicate filter) {
+ Objects.requireNonNull(filter);
+ return bulkRemove(filter);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean removeAll(Collection c) {
+ Objects.requireNonNull(c);
+ return bulkRemove(e -> c.contains(e));
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean retainAll(Collection c) {
+ Objects.requireNonNull(c);
+ return bulkRemove(e -> !c.contains(e));
+ }
+
+ /** Implementation of bulk remove methods. */
+ private boolean bulkRemove(Predicate filter) {
+ // checkInvariants();
+ final Object[] es = elements;
+ final int capacity = es.length;
+ int i = head, j = i, remaining = size, deleted = 0;
+ try {
+ for (; remaining > 0; remaining--) {
+ @SuppressWarnings("unchecked") E e = (E) es[i];
+ if (filter.test(e))
+ deleted++;
+ else {
+ if (j != i)
+ es[j] = e;
+ if (++j >= capacity) j = 0;
+ }
+ if (++i >= capacity) i = 0;
+ }
+ return deleted > 0;
+ } catch (Throwable ex) {
+ if (deleted > 0)
+ for (; remaining > 0; remaining--) {
+ es[j] = es[i];
+ if (++i >= capacity) i = 0;
+ if (++j >= capacity) j = 0;
+ }
+ throw ex;
+ } finally {
+ size -= deleted;
+ circularClear(es, j, deleted);
+ // checkInvariants();
+ }
+ }
+
+ /**
+ * 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;
- while ( (x = elements[i]) != null) {
- if (o.equals(x))
- return true;
- i = (i + 1) & mask;
+ if (o != null) {
+ final Object[] es = elements;
+ int i, end, to, todo;
+ todo = (end = (i = head) + size)
+ - (to = (es.length - end >= 0) ? end : es.length);
+ for (;; to = todo, i = 0, todo = 0) {
+ for (; i < to; i++)
+ if (o.equals(es[i]))
+ return true;
+ if (todo == 0) break;
+ }
}
return false;
}
/**
* Removes a single instance of the specified element from this deque.
- * This method is equivalent to {@link #removeFirstOccurrence}.
+ * If the deque does not contain the element, it is unchanged.
+ * 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(Object)}.
*
- * @param e element to be removed from this deque, if present
- * @return true if this deque contained the specified element
+ * @param o element to be removed from this deque, if present
+ * @return {@code true} if this deque contained the specified element
*/
- public boolean remove(Object e) {
- return removeFirstOccurrence(e);
+ public boolean remove(Object o) {
+ return removeFirstOccurrence(o);
}
/**
* Removes all of the elements from this deque.
+ * The deque will be empty after this call returns.
*/
public void clear() {
- int h = head;
- int t = tail;
- if (h != t) { // clear all cells
- head = tail = 0;
- int i = h;
- int mask = elements.length - 1;
- do {
- elements[i] = null;
- i = (i + 1) & mask;
- } while(i != t);
+ circularClear(elements, head, size);
+ size = head = 0;
+ // checkInvariants();
+ }
+
+ /**
+ * Nulls out count elements, starting at array index from.
+ */
+ private static void circularClear(Object[] es, int from, int count) {
+ int end, to, todo;
+ todo = (end = from + count)
+ - (to = (es.length - end >= 0) ? end : es.length);
+ for (;; to = todo, from = 0, todo = 0) {
+ Arrays.fill(es, from, to, null);
+ if (todo == 0) break;
}
}
/**
* Returns an array containing all of the elements in this deque
- * in the correct order.
+ * in proper sequence (from first to last element).
+ *
+ *
The returned array will be "safe" in that no references to it are
+ * maintained by this deque. (In other words, this method must allocate
+ * a new array). The caller is thus free to modify the returned array.
+ *
+ *
This method acts as bridge between array-based and collection-based
+ * APIs.
*
* @return an array containing all of the elements in this deque
- * in the correct order
*/
public Object[] toArray() {
- return copyElements(new Object[size()]);
+ return toArray(Object[].class);
+ }
+
+ private T[] toArray(Class klazz) {
+ final Object[] es = elements;
+ final T[] a;
+ final int head, len, end, todo;
+ todo = size - (len = Math.min(size, es.length - (head = this.head)));
+ if ((end = head + size) >= 0) {
+ a = Arrays.copyOfRange(es, head, end, klazz);
+ } else {
+ // integer overflow!
+ a = Arrays.copyOfRange(es, 0, size, klazz);
+ System.arraycopy(es, head, a, 0, len);
+ }
+ if (todo > 0)
+ System.arraycopy(es, 0, a, len, todo);
+ return a;
}
/**
- * Returns an array containing all of the elements in this deque in the
- * correct order; the runtime type of the returned array is that of the
- * specified array. If the deque fits in the specified array, it is
- * returned therein. Otherwise, a new array is allocated with the runtime
- * type of the specified array and the size of this deque.
+ * Returns an array containing all of the elements in this deque in
+ * proper sequence (from first to last element); the runtime type of the
+ * returned array is that of the specified array. If the deque fits in
+ * the specified array, it is returned therein. Otherwise, a new array
+ * is allocated with the runtime type of the specified array and the
+ * size of this deque.
+ *
+ * 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
+ * {@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 {@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 {@code String}:
*
- *
If the deque fits in the specified array with room to spare (i.e.,
- * the array has more elements than the deque), the element in the array
- * immediately following the end of the collection is set to null.
+ *
{@code String[] y = x.toArray(new String[0]);}
+ *
+ * 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
- * same runtime type is allocated for this purpose
- * @return an array containing the elements of the deque
- * @throws ArrayStoreException if the runtime type of a is not a supertype
- * of the runtime type of every element in this deque
+ * be stored, if it is big enough; otherwise, a new array of the
+ * same runtime type is allocated for this purpose
+ * @return an array containing all of the elements in this deque
+ * @throws ArrayStoreException if the runtime type of the specified array
+ * is not a supertype of the runtime type of every element in
+ * 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);
- if (a.length > size)
+ final int size;
+ if ((size = this.size) > a.length)
+ return toArray((Class) a.getClass());
+ final Object[] es = elements;
+ int i, j, len, todo;
+ todo = size - (len = Math.min(size, es.length - (i = head)));
+ for (j = 0;; j += len, len = todo, todo = 0, i = 0) {
+ System.arraycopy(es, i, a, j, len);
+ if (todo == 0) break;
+ }
+ if (size < a.length)
a[size] = null;
return a;
}
@@ -723,61 +1132,82 @@ 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,
+ * @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.
*/
- private void writeObject(ObjectOutputStream s) throws IOException {
+ private void writeObject(java.io.ObjectOutputStream s)
+ throws java.io.IOException {
s.defaultWriteObject();
// Write out size
- int size = size();
s.writeInt(size);
// Write out elements in order.
- int i = head;
- int mask = elements.length - 1;
- for (int j = 0; j < size; j++) {
- s.writeObject(elements[i]);
- i = (i + 1) & mask;
+ final Object[] es = elements;
+ int i, end, to, todo;
+ todo = (end = (i = head) + size)
+ - (to = (es.length - end >= 0) ? end : es.length);
+ for (;; to = todo, i = 0, todo = 0) {
+ for (; i < to; i++)
+ s.writeObject(es[i]);
+ if (todo == 0) break;
}
}
/**
- * Deserialize this deque.
+ * 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(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
- int size = s.readInt();
- allocateElements(size);
- head = 0;
- tail = size;
+ elements = new Object[size = s.readInt()];
// Read in all elements in the proper order.
for (int i = 0; i < size; i++)
- elements[i] = (E)s.readObject();
+ elements[i] = s.readObject();
+ }
+ /** debugging */
+ void checkInvariants() {
+ try {
+ int capacity = elements.length;
+ // assert size >= 0 && size <= capacity;
+ // assert head >= 0;
+ // assert capacity == 0 || head < capacity;
+ // assert size == 0 || elements[head] != null;
+ // assert size == 0 || elements[tail()] != null;
+ // assert size == capacity || elements[dec(head, capacity)] == null;
+ // assert size == capacity || elements[inc(tail(), capacity)] == null;
+ } catch (Throwable t) {
+ System.err.printf("head=%d size=%d capacity=%d%n",
+ head, size, elements.length);
+ System.err.printf("elements=%s%n",
+ Arrays.toString(elements));
+ throw t;
+ }
}
+
}