Android: remove unintentional reliance on API 9

The AsyncTask class we took from android source makes use of ArrayDeque
which in turn makes use of Deque, neither of which are available below
API 9. Fix is to take these two classes from android source also

3 files changed, 1410 insertions, 1 deletions

diff --git a/android/src/com/artifex/mupdfdemo/ArrayDeque.java b/android/src/com/artifex/mupdfdemo/ArrayDeque.java
new file mode 100644
index 00000000..a66c63b5
--- /dev/null
+++ b/android/src/com/artifex/mupdfdemo/ArrayDeque.java
@@ -0,0 +1,856 @@
+/*
+ * Written by Josh Bloch of Google Inc. and released to the public domain,
+ * as explained at http://creativecommons.org/publicdomain/zero/1.0/.
+ */
+
+package com.artifex.mupdfdemo;
+
+import java.util.AbstractCollection;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.ConcurrentModificationException;
+import java.util.Deque;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.Queue;
+import java.util.Stack;
+
+// BEGIN android-note
+// removed link to collections framework docs
+// END android-note
+
+/**
+ * Resizable-array implementation of the {@link Deque} interface.  Array
+ * deques have no capacity restrictions; they grow as necessary to support
+ * usage.  They are not thread-safe; in the absence of external
+ * synchronization, they do not support concurrent access by multiple threads.
+ * Null elements are prohibited.  This class is likely to be faster than
+ * {@link Stack} when used as a stack, and faster than {@link LinkedList}
+ * when used as a queue.
+ *
+ * <p>Most <tt>ArrayDeque</tt> 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.
+ *
+ * <p>The iterators returned by this class's <tt>iterator</tt> 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 <tt>remove</tt>
+ * 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.
+ *
+ * <p>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 <tt>ConcurrentModificationException</tt> on a best-effort basis.
+ * Therefore, it would be wrong to write a program that depended on this
+ * exception for its correctness: <i>the fail-fast behavior of iterators
+ * should be used only to detect bugs.</i>
+ *
+ * <p>This class and its iterator implement all of the
+ * <em>optional</em> methods of the {@link Collection} and {@link
+ * Iterator} interfaces.
+ *
+ * @author  Josh Bloch and Doug Lea
+ * @since   1.6
+ * @param <E> the type of elements held in this collection
+ */
+public class ArrayDeque<E> extends AbstractCollection<E>
+                           implements Deque<E>, Cloneable, java.io.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.
+     */
+    private 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.
+     */
+    private static final int MIN_INITIAL_CAPACITY = 8;
+
+    // ******  Array allocation and resizing utilities ******
+
+    /**
+     * 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++;
+
+            if (initialCapacity < 0)   // Too many elements, must back off
+                initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
+        }
+        elements = new Object[initialCapacity];
+    }
+
+    /**
+     * Double the capacity of this deque.  Call only when full, i.e.,
+     * when head and tail have wrapped around to become equal.
+     */
+    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 = a;
+        head = 0;
+        tail = n;
+    }
+
+    /**
+     * 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.
+     */
+    public ArrayDeque() {
+        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
+     */
+    public ArrayDeque(int numElements) {
+        allocateElements(numElements);
+    }
+
+    /**
+     * Constructs a deque containing the elements of the specified
+     * collection, in the order they are returned by the collection's
+     * iterator.  (The first element returned by the collection's
+     * iterator becomes the first element, or <i>front</i> of the
+     * deque.)
+     *
+     * @param c the collection whose elements are to be placed into the deque
+     * @throws NullPointerException if the specified collection is null
+     */
+    public ArrayDeque(Collection<? extends E> c) {
+        allocateElements(c.size());
+        addAll(c);
+    }
+
+    // The main insertion and extraction methods are addFirst,
+    // addLast, pollFirst, pollLast. The other methods are defined in
+    // terms of these.
+
+    /**
+     * Inserts the specified element at the front of this deque.
+     *
+     * @param e the element to add
+     * @throws NullPointerException if the specified element is null
+     */
+    public void addFirst(E e) {
+        if (e == null)
+            throw new NullPointerException("e == null");
+        elements[head = (head - 1) & (elements.length - 1)] = e;
+        if (head == tail)
+            doubleCapacity();
+    }
+
+    /**
+     * Inserts the specified element at the end of this deque.
+     *
+     * <p>This method is equivalent to {@link #add}.
+     *
+     * @param e the element to add
+     * @throws NullPointerException if the specified element is null
+     */
+    public void addLast(E e) {
+        if (e == null)
+            throw new NullPointerException("e == null");
+        elements[tail] = e;
+        if ( (tail = (tail + 1) & (elements.length - 1)) == head)
+            doubleCapacity();
+    }
+
+    /**
+     * Inserts the specified element at the front of this deque.
+     *
+     * @param e the element to add
+     * @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean offerFirst(E e) {
+        addFirst(e);
+        return true;
+    }
+
+    /**
+     * Inserts the specified element at the end of this deque.
+     *
+     * @param e the element to add
+     * @return <tt>true</tt> (as specified by {@link Deque#offerLast})
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean offerLast(E e) {
+        addLast(e);
+        return true;
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E removeFirst() {
+        E x = pollFirst();
+        if (x == null)
+            throw new NoSuchElementException();
+        return x;
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E removeLast() {
+        E x = pollLast();
+        if (x == null)
+            throw new NoSuchElementException();
+        return x;
+    }
+
+    public E pollFirst() {
+        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);
+        return result;
+    }
+
+    public E pollLast() {
+        int t = (tail - 1) & (elements.length - 1);
+        @SuppressWarnings("unchecked") E result = (E) elements[t];
+        if (result == null)
+            return null;
+        elements[t] = null;
+        tail = t;
+        return result;
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E getFirst() {
+        @SuppressWarnings("unchecked") E result = (E) elements[head];
+        if (result == null)
+            throw new NoSuchElementException();
+        return result;
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E getLast() {
+        @SuppressWarnings("unchecked")
+        E result = (E) elements[(tail - 1) & (elements.length - 1)];
+        if (result == null)
+            throw new NoSuchElementException();
+        return result;
+    }
+
+    public E peekFirst() {
+        @SuppressWarnings("unchecked") E result = (E) elements[head];
+        // elements[head] is null if deque empty
+        return result;
+    }
+
+    public E peekLast() {
+        @SuppressWarnings("unchecked")
+        E result = (E) elements[(tail - 1) & (elements.length - 1)];
+        return result;
+    }
+
+    /**
+     * 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 <tt>e</tt> such that
+     * <tt>o.equals(e)</tt> (if such an element exists).
+     * Returns <tt>true</tt> 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 <tt>true</tt> 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;
+            }
+            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).
+     * If the deque does not contain the element, it is unchanged.
+     * More formally, removes the last element <tt>e</tt> such that
+     * <tt>o.equals(e)</tt> (if such an element exists).
+     * Returns <tt>true</tt> 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 <tt>true</tt> 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;
+            }
+            i = (i - 1) & mask;
+        }
+        return false;
+    }
+
+    // *** Queue methods ***
+
+    /**
+     * Inserts the specified element at the end of this deque.
+     *
+     * <p>This method is equivalent to {@link #addLast}.
+     *
+     * @param e the element to add
+     * @return <tt>true</tt> (as specified by {@link Collection#add})
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean add(E e) {
+        addLast(e);
+        return true;
+    }
+
+    /**
+     * Inserts the specified element at the end of this deque.
+     *
+     * <p>This method is equivalent to {@link #offerLast}.
+     *
+     * @param e the element to add
+     * @return <tt>true</tt> (as specified by {@link Queue#offer})
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean offer(E e) {
+        return offerLast(e);
+    }
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque.
+     *
+     * This method differs from {@link #poll poll} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #removeFirst}.
+     *
+     * @return the head of the queue represented by this deque
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E remove() {
+        return removeFirst();
+    }
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque
+     * (in other words, the first element of this deque), or returns
+     * <tt>null</tt> if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #pollFirst}.
+     *
+     * @return the head of the queue represented by this deque, or
+     *         <tt>null</tt> if this deque is empty
+     */
+    public E poll() {
+        return pollFirst();
+    }
+
+    /**
+     * Retrieves, but does not remove, the head of the queue represented by
+     * this deque.  This method differs from {@link #peek peek} only in
+     * that it throws an exception if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #getFirst}.
+     *
+     * @return the head of the queue represented by this deque
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E element() {
+        return getFirst();
+    }
+
+    /**
+     * Retrieves, but does not remove, the head of the queue represented by
+     * this deque, or returns <tt>null</tt> if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #peekFirst}.
+     *
+     * @return the head of the queue represented by this deque, or
+     *         <tt>null</tt> if this deque is empty
+     */
+    public E peek() {
+        return peekFirst();
+    }
+
+    // *** Stack methods ***
+
+    /**
+     * Pushes an element onto the stack represented by this deque.  In other
+     * words, inserts the element at the front of this deque.
+     *
+     * <p>This method is equivalent to {@link #addFirst}.
+     *
+     * @param e the element to push
+     * @throws NullPointerException if the specified element is null
+     */
+    public void push(E e) {
+        addFirst(e);
+    }
+
+    /**
+     * Pops an element from the stack represented by this deque.  In other
+     * words, removes and returns the first element of this deque.
+     *
+     * <p>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 {@inheritDoc}
+     */
+    public E pop() {
+        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
+     * elements backwards or forwards in the array.
+     *
+     * <p>This method is called delete rather than remove to emphasize
+     * that its semantics differ from those of {@link List#remove(int)}.
+     *
+     * @return true if elements moved backwards
+     */
+    private boolean delete(int i) {
+        //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 {
+            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 ***
+
+    /**
+     * Returns the number of elements in this deque.
+     *
+     * @return the number of elements in this deque
+     */
+    public int size() {
+        return (tail - head) & (elements.length - 1);
+    }
+
+    /**
+     * Returns <tt>true</tt> if this deque contains no elements.
+     *
+     * @return <tt>true</tt> if this deque contains no elements
+     */
+    public boolean isEmpty() {
+        return head == tail;
+    }
+
+    /**
+     * Returns an iterator over the elements in this deque.  The elements
+     * will be ordered from first (head) to last (tail).  This is the same
+     * 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
+     */
+    public Iterator<E> iterator() {
+        return new DeqIterator();
+    }
+
+    public Iterator<E> descendingIterator() {
+        return new DescendingIterator();
+    }
+
+    private class DeqIterator implements Iterator<E> {
+        /**
+         * Index of element to be returned by subsequent call to next.
+         */
+        private int cursor = head;
+
+        /**
+         * Tail recorded at construction (also in remove), to stop
+         * iterator and also to check for comodification.
+         */
+        private int fence = tail;
+
+        /**
+         * 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;
+
+        public boolean hasNext() {
+            return cursor != fence;
+        }
+
+        public E next() {
+            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 == null)
+                throw new ConcurrentModificationException();
+            lastRet = cursor;
+            cursor = (cursor + 1) & (elements.length - 1);
+            return result;
+        }
+
+        public void remove() {
+            if (lastRet < 0)
+                throw new IllegalStateException();
+            if (delete(lastRet)) { // if left-shifted, undo increment in next()
+                cursor = (cursor - 1) & (elements.length - 1);
+                fence = tail;
+            }
+            lastRet = -1;
+        }
+    }
+
+    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;
+
+        public boolean hasNext() {
+            return cursor != fence;
+        }
+
+        public E next() {
+            if (cursor == fence)
+                throw new NoSuchElementException();
+            cursor = (cursor - 1) & (elements.length - 1);
+            @SuppressWarnings("unchecked") E result = (E) elements[cursor];
+            if (head != fence || result == null)
+                throw new ConcurrentModificationException();
+            lastRet = cursor;
+            return result;
+        }
+
+        public void remove() {
+            if (lastRet < 0)
+                throw new IllegalStateException();
+            if (!delete(lastRet)) {
+                cursor = (cursor + 1) & (elements.length - 1);
+                fence = head;
+            }
+            lastRet = -1;
+        }
+    }
+
+    /**
+     * Returns <tt>true</tt> if this deque contains the specified element.
+     * More formally, returns <tt>true</tt> if and only if this deque contains
+     * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
+     *
+     * @param o object to be checked for containment in this deque
+     * @return <tt>true</tt> 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;
+        }
+        return false;
+    }
+
+    /**
+     * 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 <tt>e</tt> such that
+     * <tt>o.equals(e)</tt> (if such an element exists).
+     * Returns <tt>true</tt> if this deque contained the specified element
+     * (or equivalently, if this deque changed as a result of the call).
+     *
+     * <p>This method is equivalent to {@link #removeFirstOccurrence}.
+     *
+     * @param o element to be removed from this deque, if present
+     * @return <tt>true</tt> if this deque contained the specified element
+     */
+    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);
+        }
+    }
+
+    /**
+     * Returns an array containing all of the elements in this deque
+     * in proper sequence (from first to last element).
+     *
+     * <p>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.
+     *
+     * <p>This method acts as bridge between array-based and collection-based
+     * APIs.
+     *
+     * @return an array containing all of the elements in this deque
+     */
+    public Object[] toArray() {
+        return copyElements(new Object[size()]);
+    }
+
+    /**
+     * 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.
+     *
+     * <p>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
+     * <tt>null</tt>.
+     *
+     * <p>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.
+     *
+     * <p>Suppose <tt>x</tt> is a deque known to contain only strings.
+     * The following code can be used to dump the deque into a newly
+     * allocated array of <tt>String</tt>:
+     *
+     *  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
+     *
+     * Note that <tt>toArray(new Object[0])</tt> is identical in function to
+     * <tt>toArray()</tt>.
+     *
+     * @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 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> 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;
+        return a;
+    }
+
+    // *** Object methods ***
+
+    /**
+     * Returns a copy of this deque.
+     *
+     * @return a copy of this deque
+     */
+    public ArrayDeque<E> clone() {
+        try {
+            @SuppressWarnings("unchecked")
+            ArrayDeque<E> result = (ArrayDeque<E>) 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.
+     *
+     * @serialData The current size (<tt>int</tt>) of the deque,
+     * followed by all of its elements (each an object reference) in
+     * first-to-last order.
+     */
+    private void writeObject(java.io.ObjectOutputStream s)
+            throws java.io.IOException {
+        s.defaultWriteObject();
+
+        // Write out size
+        s.writeInt(size());
+
+        // Write out elements in order.
+        int mask = elements.length - 1;
+        for (int i = head; i != tail; i = (i + 1) & mask)
+            s.writeObject(elements[i]);
+    }
+
+    /**
+     * Deserialize this deque.
+     */
+    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;
+
+        // Read in all elements in the proper order.
+        for (int i = 0; i < size; i++)
+            elements[i] = s.readObject();
+    }
+}
diff --git a/android/src/com/artifex/mupdfdemo/AsyncTask.java b/android/src/com/artifex/mupdfdemo/AsyncTask.java
index 67baf62a..b370794c 100644
--- a/android/src/com/artifex/mupdfdemo/AsyncTask.java
+++ b/android/src/com/artifex/mupdfdemo/AsyncTask.java
@@ -16,7 +16,6 @@
 
 package com.artifex.mupdfdemo;
 
-import java.util.ArrayDeque;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CancellationException;
diff --git a/android/src/com/artifex/mupdfdemo/Deque.java b/android/src/com/artifex/mupdfdemo/Deque.java
new file mode 100644
index 00000000..4bb176b2
--- /dev/null
+++ b/android/src/com/artifex/mupdfdemo/Deque.java
@@ -0,0 +1,554 @@
+/*
+ * Written by Doug Lea and Josh Bloch with assistance from members of
+ * JCP JSR-166 Expert Group and released to the public domain, as explained
+ * at http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package com.artifex.mupdfdemo;
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.Queue;
+import java.util.Stack;
+
+// BEGIN android-note
+// removed link to collections framework docs
+// END android-note
+
+/**
+ * A linear collection that supports element insertion and removal at
+ * both ends.  The name <i>deque</i> is short for "double ended queue"
+ * and is usually pronounced "deck".  Most <tt>Deque</tt>
+ * implementations place no fixed limits on the number of elements
+ * they may contain, but this interface supports capacity-restricted
+ * deques as well as those with no fixed size limit.
+ *
+ * <p>This interface defines methods to access the elements at both
+ * ends of the deque.  Methods are provided to insert, remove, and
+ * examine the element.  Each of these methods exists in two forms:
+ * one throws an exception if the operation fails, the other returns a
+ * special value (either <tt>null</tt> or <tt>false</tt>, depending on
+ * the operation).  The latter form of the insert operation is
+ * designed specifically for use with capacity-restricted
+ * <tt>Deque</tt> implementations; in most implementations, insert
+ * operations cannot fail.
+ *
+ * <p>The twelve methods described above are summarized in the
+ * following table:
+ *
+ * <p>
+ * <table BORDER CELLPADDING=3 CELLSPACING=1>
+ *  <tr>
+ *    <td></td>
+ *    <td ALIGN=CENTER COLSPAN = 2> <b>First Element (Head)</b></td>
+ *    <td ALIGN=CENTER COLSPAN = 2> <b>Last Element (Tail)</b></td>
+ *  </tr>
+ *  <tr>
+ *    <td></td>
+ *    <td ALIGN=CENTER><em>Throws exception</em></td>
+ *    <td ALIGN=CENTER><em>Special value</em></td>
+ *    <td ALIGN=CENTER><em>Throws exception</em></td>
+ *    <td ALIGN=CENTER><em>Special value</em></td>
+ *  </tr>
+ *  <tr>
+ *    <td><b>Insert</b></td>
+ *    <td>{@link #addFirst addFirst(e)}</td>
+ *    <td>{@link #offerFirst offerFirst(e)}</td>
+ *    <td>{@link #addLast addLast(e)}</td>
+ *    <td>{@link #offerLast offerLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <td><b>Remove</b></td>
+ *    <td>{@link #removeFirst removeFirst()}</td>
+ *    <td>{@link #pollFirst pollFirst()}</td>
+ *    <td>{@link #removeLast removeLast()}</td>
+ *    <td>{@link #pollLast pollLast()}</td>
+ *  </tr>
+ *  <tr>
+ *    <td><b>Examine</b></td>
+ *    <td>{@link #getFirst getFirst()}</td>
+ *    <td>{@link #peekFirst peekFirst()}</td>
+ *    <td>{@link #getLast getLast()}</td>
+ *    <td>{@link #peekLast peekLast()}</td>
+ *  </tr>
+ * </table>
+ *
+ * <p>This interface extends the {@link Queue} interface.  When a deque is
+ * used as a queue, FIFO (First-In-First-Out) behavior results.  Elements are
+ * added at the end of the deque and removed from the beginning.  The methods
+ * inherited from the <tt>Queue</tt> interface are precisely equivalent to
+ * <tt>Deque</tt> methods as indicated in the following table:
+ *
+ * <p>
+ * <table BORDER CELLPADDING=3 CELLSPACING=1>
+ *  <tr>
+ *    <td ALIGN=CENTER> <b><tt>Queue</tt> Method</b></td>
+ *    <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link java.util.Queue#add add(e)}</td>
+ *    <td>{@link #addLast addLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link java.util.Queue#offer offer(e)}</td>
+ *    <td>{@link #offerLast offerLast(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link java.util.Queue#remove remove()}</td>
+ *    <td>{@link #removeFirst removeFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link java.util.Queue#poll poll()}</td>
+ *    <td>{@link #pollFirst pollFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link java.util.Queue#element element()}</td>
+ *    <td>{@link #getFirst getFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link java.util.Queue#peek peek()}</td>
+ *    <td>{@link #peek peekFirst()}</td>
+ *  </tr>
+ * </table>
+ *
+ * <p>Deques can also be used as LIFO (Last-In-First-Out) stacks.  This
+ * interface should be used in preference to the legacy {@link Stack} class.
+ * When a deque is used as a stack, elements are pushed and popped from the
+ * beginning of the deque.  Stack methods are precisely equivalent to
+ * <tt>Deque</tt> methods as indicated in the table below:
+ *
+ * <p>
+ * <table BORDER CELLPADDING=3 CELLSPACING=1>
+ *  <tr>
+ *    <td ALIGN=CENTER> <b>Stack Method</b></td>
+ *    <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link #push push(e)}</td>
+ *    <td>{@link #addFirst addFirst(e)}</td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link #pop pop()}</td>
+ *    <td>{@link #removeFirst removeFirst()}</td>
+ *  </tr>
+ *  <tr>
+ *    <td>{@link #peek peek()}</td>
+ *    <td>{@link #peekFirst peekFirst()}</td>
+ *  </tr>
+ * </table>
+ *
+ * <p>Note that the {@link #peek peek} method works equally well when
+ * a deque is used as a queue or a stack; in either case, elements are
+ * drawn from the beginning of the deque.
+ *
+ * <p>This interface provides two methods to remove interior
+ * elements, {@link #removeFirstOccurrence removeFirstOccurrence} and
+ * {@link #removeLastOccurrence removeLastOccurrence}.
+ *
+ * <p>Unlike the {@link List} interface, this interface does not
+ * provide support for indexed access to elements.
+ *
+ * <p>While <tt>Deque</tt> implementations are not strictly required
+ * to prohibit the insertion of null elements, they are strongly
+ * encouraged to do so.  Users of any <tt>Deque</tt> implementations
+ * that do allow null elements are strongly encouraged <i>not</i> to
+ * take advantage of the ability to insert nulls.  This is so because
+ * <tt>null</tt> is used as a special return value by various methods
+ * to indicated that the deque is empty.
+ *
+ * <p><tt>Deque</tt> implementations generally do not define
+ * element-based versions of the <tt>equals</tt> and <tt>hashCode</tt>
+ * methods, but instead inherit the identity-based versions from class
+ * <tt>Object</tt>.
+ *
+ * @author Doug Lea
+ * @author Josh Bloch
+ * @since  1.6
+ * @param <E> the type of elements held in this collection
+ */
+
+public interface Deque<E> extends Queue<E> {
+    /**
+     * Inserts the specified element at the front of this deque if it is
+     * possible to do so immediately without violating capacity restrictions.
+     * When using a capacity-restricted deque, it is generally preferable to
+     * use method {@link #offerFirst}.
+     *
+     * @param e the element to add
+     * @throws IllegalStateException if the element cannot be added at this
+     *         time due to capacity restrictions
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    void addFirst(E e);
+
+    /**
+     * Inserts the specified element at the end of this deque if it is
+     * possible to do so immediately without violating capacity restrictions.
+     * When using a capacity-restricted deque, it is generally preferable to
+     * use method {@link #offerLast}.
+     *
+     * <p>This method is equivalent to {@link #add}.
+     *
+     * @param e the element to add
+     * @throws IllegalStateException if the element cannot be added at this
+     *         time due to capacity restrictions
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    void addLast(E e);
+
+    /**
+     * Inserts the specified element at the front of this deque unless it would
+     * violate capacity restrictions.  When using a capacity-restricted deque,
+     * this method is generally preferable to the {@link #addFirst} method,
+     * which can fail to insert an element only by throwing an exception.
+     *
+     * @param e the element to add
+     * @return <tt>true</tt> if the element was added to this deque, else
+     *         <tt>false</tt>
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offerFirst(E e);
+
+    /**
+     * Inserts the specified element at the end of this deque unless it would
+     * violate capacity restrictions.  When using a capacity-restricted deque,
+     * this method is generally preferable to the {@link #addLast} method,
+     * which can fail to insert an element only by throwing an exception.
+     *
+     * @param e the element to add
+     * @return <tt>true</tt> if the element was added to this deque, else
+     *         <tt>false</tt>
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offerLast(E e);
+
+    /**
+     * Retrieves and removes the first element of this deque.  This method
+     * differs from {@link #pollFirst pollFirst} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * @return the head of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E removeFirst();
+
+    /**
+     * Retrieves and removes the last element of this deque.  This method
+     * differs from {@link #pollLast pollLast} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * @return the tail of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E removeLast();
+
+    /**
+     * Retrieves and removes the first element of this deque,
+     * or returns <tt>null</tt> if this deque is empty.
+     *
+     * @return the head of this deque, or <tt>null</tt> if this deque is empty
+     */
+    E pollFirst();
+
+    /**
+     * Retrieves and removes the last element of this deque,
+     * or returns <tt>null</tt> if this deque is empty.
+     *
+     * @return the tail of this deque, or <tt>null</tt> if this deque is empty
+     */
+    E pollLast();
+
+    /**
+     * Retrieves, but does not remove, the first element of this deque.
+     *
+     * This method differs from {@link #peekFirst peekFirst} only in that it
+     * throws an exception if this deque is empty.
+     *
+     * @return the head of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E getFirst();
+
+    /**
+     * Retrieves, but does not remove, the last element of this deque.
+     * This method differs from {@link #peekLast peekLast} only in that it
+     * throws an exception if this deque is empty.
+     *
+     * @return the tail of this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E getLast();
+
+    /**
+     * Retrieves, but does not remove, the first element of this deque,
+     * or returns <tt>null</tt> if this deque is empty.
+     *
+     * @return the head of this deque, or <tt>null</tt> if this deque is empty
+     */
+    E peekFirst();
+
+    /**
+     * Retrieves, but does not remove, the last element of this deque,
+     * or returns <tt>null</tt> if this deque is empty.
+     *
+     * @return the tail of this deque, or <tt>null</tt> if this deque is empty
+     */
+    E peekLast();
+
+    /**
+     * Removes the first occurrence of the specified element from this deque.
+     * If the deque does not contain the element, it is unchanged.
+     * More formally, removes the first element <tt>e</tt> such that
+     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
+     * (if such an element exists).
+     * Returns <tt>true</tt> 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 <tt>true</tt> if an element was removed as a result of this call
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this deque (optional)
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements (optional)
+     */
+    boolean removeFirstOccurrence(Object o);
+
+    /**
+     * Removes the last occurrence of the specified element from this deque.
+     * If the deque does not contain the element, it is unchanged.
+     * More formally, removes the last element <tt>e</tt> such that
+     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
+     * (if such an element exists).
+     * Returns <tt>true</tt> 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 <tt>true</tt> if an element was removed as a result of this call
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this deque (optional)
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements (optional)
+     */
+    boolean removeLastOccurrence(Object o);
+
+    // *** Queue methods ***
+
+    /**
+     * Inserts the specified element into the queue represented by this deque
+     * (in other words, at the tail of this deque) if it is possible to do so
+     * immediately without violating capacity restrictions, returning
+     * <tt>true</tt> upon success and throwing an
+     * <tt>IllegalStateException</tt> if no space is currently available.
+     * When using a capacity-restricted deque, it is generally preferable to
+     * use {@link #offer(Object) offer}.
+     *
+     * <p>This method is equivalent to {@link #addLast}.
+     *
+     * @param e the element to add
+     * @return <tt>true</tt> (as specified by {@link Collection#add})
+     * @throws IllegalStateException if the element cannot be added at this
+     *         time due to capacity restrictions
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean add(E e);
+
+    /**
+     * Inserts the specified element into the queue represented by this deque
+     * (in other words, at the tail of this deque) if it is possible to do so
+     * immediately without violating capacity restrictions, returning
+     * <tt>true</tt> upon success and <tt>false</tt> if no space is currently
+     * available.  When using a capacity-restricted deque, this method is
+     * generally preferable to the {@link #add} method, which can fail to
+     * insert an element only by throwing an exception.
+     *
+     * <p>This method is equivalent to {@link #offerLast}.
+     *
+     * @param e the element to add
+     * @return <tt>true</tt> if the element was added to this deque, else
+     *         <tt>false</tt>
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    boolean offer(E e);
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque
+     * (in other words, the first element of this deque).
+     * This method differs from {@link #poll poll} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #removeFirst()}.
+     *
+     * @return the head of the queue represented by this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E remove();
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque
+     * (in other words, the first element of this deque), or returns
+     * <tt>null</tt> if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #pollFirst()}.
+     *
+     * @return the first element of this deque, or <tt>null</tt> if
+     *         this deque is empty
+     */
+    E poll();
+
+    /**
+     * Retrieves, but does not remove, the head of the queue represented by
+     * this deque (in other words, the first element of this deque).
+     * This method differs from {@link #peek peek} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #getFirst()}.
+     *
+     * @return the head of the queue represented by this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    E element();
+
+    /**
+     * Retrieves, but does not remove, the head of the queue represented by
+     * this deque (in other words, the first element of this deque), or
+     * returns <tt>null</tt> if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #peekFirst()}.
+     *
+     * @return the head of the queue represented by this deque, or
+     *         <tt>null</tt> if this deque is empty
+     */
+    E peek();
+
+
+    // *** Stack methods ***
+
+    /**
+     * Pushes an element onto the stack represented by this deque (in other
+     * words, at the head of this deque) if it is possible to do so
+     * immediately without violating capacity restrictions, returning
+     * <tt>true</tt> upon success and throwing an
+     * <tt>IllegalStateException</tt> if no space is currently available.
+     *
+     * <p>This method is equivalent to {@link #addFirst}.
+     *
+     * @param e the element to push
+     * @throws IllegalStateException if the element cannot be added at this
+     *         time due to capacity restrictions
+     * @throws ClassCastException if the class of the specified element
+     *         prevents it from being added to this deque
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements
+     * @throws IllegalArgumentException if some property of the specified
+     *         element prevents it from being added to this deque
+     */
+    void push(E e);
+
+    /**
+     * Pops an element from the stack represented by this deque.  In other
+     * words, removes and returns the first element of this deque.
+     *
+     * <p>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
+     */
+    E pop();
+
+
+    // *** Collection methods ***
+
+    /**
+     * Removes the first occurrence of the specified element from this deque.
+     * If the deque does not contain the element, it is unchanged.
+     * More formally, removes the first element <tt>e</tt> such that
+     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
+     * (if such an element exists).
+     * Returns <tt>true</tt> if this deque contained the specified element
+     * (or equivalently, if this deque changed as a result of the call).
+     *
+     * <p>This method is equivalent to {@link #removeFirstOccurrence}.
+     *
+     * @param o element to be removed from this deque, if present
+     * @return <tt>true</tt> if an element was removed as a result of this call
+     * @throws ClassCastException if the class of the specified element
+     *         is incompatible with this deque (optional)
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements (optional)
+     */
+    boolean remove(Object o);
+
+    /**
+     * Returns <tt>true</tt> if this deque contains the specified element.
+     * More formally, returns <tt>true</tt> if and only if this deque contains
+     * at least one element <tt>e</tt> such that
+     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
+     *
+     * @param o element whose presence in this deque is to be tested
+     * @return <tt>true</tt> if this deque contains the specified element
+     * @throws ClassCastException if the type of the specified element
+     *         is incompatible with this deque (optional)
+     * @throws NullPointerException if the specified element is null and this
+     *         deque does not permit null elements (optional)
+     */
+    boolean contains(Object o);
+
+    /**
+     * Returns the number of elements in this deque.
+     *
+     * @return the number of elements in this deque
+     */
+    public int size();
+
+    /**
+     * Returns an iterator over the elements in this deque in proper sequence.
+     * The elements will be returned in order from first (head) to last (tail).
+     *
+     * @return an iterator over the elements in this deque in proper sequence
+     */
+    Iterator<E> iterator();
+
+    /**
+     * Returns an iterator over the elements in this deque in reverse
+     * sequential order.  The elements will be returned in order from
+     * last (tail) to first (head).
+     *
+     * @return an iterator over the elements in this deque in reverse
+     * sequence
+     */
+    Iterator<E> descendingIterator();
+
+}