java/util/PriorityQueue.java

 package java.util;

/**
 * An unbounded priority queue based on a priority heap.  This queue orders
 * elements according to an order specified at construction time, which is
 * specified in the same manner as {@link java.util.TreeSet} and
 * {@link java.util.TreeMap}: elements are ordered
 * either according to their <i>natural order</i> (see {@link Comparable}), or
 * according to a {@link java.util.Comparator}, depending on which
 * constructor is used.
 * <p>The <em>head</em> of this queue is the <em>least</em> element with
 * respect to the specified ordering.
 * If multiple elements are tied for least value, the
 * head is one of those elements. A priority queue does not permit
 * <tt>null</tt> elements.
 *
 * <p>The {@link #remove()} and {@link #poll()} methods remove and
 * return the head of the queue.
 *
 * <p>The {@link #element()} and {@link #peek()} methods return, but do
 * not delete, the head of the queue.
 *
 * <p>A priority queue has a <i>capacity</i>.  The capacity is the
 * size of the array used internally to store the elements on the
 * queue.
 * It is always at least as large as the queue size.  As
 * elements are added to a priority queue, its capacity grows
 * automatically.  The details of the growth policy are not specified.
 *
 * <p>Implementation note: this implementation provides O(log(n)) time
 * for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
 * <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
 * <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
 * constant time for the retrieval methods (<tt>peek</tt>,
 * <tt>element</tt>, and <tt>size</tt>).
 *
 * <p>This class is a member of the
 * <a href="{@docRoot}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 * @since 1.5
 * @author Josh Bloch
 */
public class PriorityQueue<E> extends AbstractQueue<E>
    implements Queue<E>, java.io.Serializable {

    private static final int DEFAULT_INITIAL_CAPACITY = 11;

    /**
     * Priority queue represented as a balanced binary heap: the two children
     * of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
     * ordered by comparator, or by the elements' natural ordering, if
     * comparator is null:  For each node n in the heap and each descendant d
     * of n, n <= d.
     *
     * The element with the lowest value is in queue[1], assuming the queue is
     * nonempty.  (A one-based array is used in preference to the traditional
     * zero-based array to simplify parent and child calculations.)
     *
     * queue.length must be >= 2, even if size == 0.
     */
    private transient Object[] queue;

    /**
     * The number of elements in the priority queue.
     */
    private int size = 0;

    /**
     * The comparator, or null if priority queue uses elements'
     * natural ordering.
     */
    private final Comparator<? super E> comparator;

    /**
     * The number of times this priority queue has been
     * <i>structurally modified</i>.  See AbstractList for gory details.
     */
    private transient int modCount = 0;

    /**
     * Creates a <tt>PriorityQueue</tt> with the default initial capacity
     * (11) that orders its elements according to their natural
     * ordering (using <tt>Comparable</tt>.)
     */
    public PriorityQueue() {
        this(DEFAULT_INITIAL_CAPACITY, null);
    }

    /**
     * Creates a <tt>PriorityQueue</tt> with the specified initial capacity
     * that orders its elements according to their natural ordering
     * (using <tt>Comparable</tt>.)
     *
     * @param initialCapacity the initial capacity for this priority queue.
     */
    public PriorityQueue(int initialCapacity) {
        this(initialCapacity, null);
    }

    /**
     * Creates a <tt>PriorityQueue</tt> with the specified initial capacity
     * that orders its elements according to the specified comparator.
     *
     * @param initialCapacity the initial capacity for this priority queue.
     * @param comparator the comparator used to order this priority queue.
     * If <tt>null</tt> then the order depends on the elements' natural
     * ordering.
     * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
     * than 1
     */
    public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
        if (initialCapacity < 1)
            throw new IllegalArgumentException();
        this.queue = new Object[initialCapacity + 1];
        this.comparator = comparator;
    }

    /**
     * Common code to initialize underlying queue array across
     * constructors below.
     */
    private void initializeArray(Collection<? extends E> c) {
        int sz = c.size();
        int initialCapacity = (int)Math.min((sz * 110L) / 100,
                                            Integer.MAX_VALUE - 1);
        if (initialCapacity < 1)
            initialCapacity = 1;

        this.queue = new Object[initialCapacity + 1];
    }

    /**
     * Initially fill elements of the queue array under the 
     * knowledge that it is sorted or is another PQ, in which
     * case we can just place the elements without fixups.
     */
    private void fillFromSorted(Collection<? extends E> c) {
        for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
            queue[++size] = i.next();
    }


    /**
     * Initially fill elements of the queue array that is
     * not to our knowledge sorted, so we must add them
     * one by one.
     */
    private void fillFromUnsorted(Collection<? extends E> c) {
        for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
            add(i.next());
    }

    /**
     * Creates a <tt>PriorityQueue</tt> containing the elements in the
     * specified collection.  The priority queue has an initial
     * capacity of 110% of the size of the specified collection or 1
     * if the collection is empty.  If the specified collection is an
     * instance of a {@link SortedSet} or is another
     * <tt>PriorityQueue</tt>, the priority queue will be sorted
     * according to the same comparator, or according to its elements'
     * natural order if the collection is sorted according to its
     * elements' natural order.  Otherwise, the priority queue is
     * ordered according to its elements' natural order.
     *
     * @param c the collection whose elements are to be placed
     *        into this priority queue.
     * @throws ClassCastException if elements of the specified collection
     *         cannot be compared to one another according to the priority
     *         queue's ordering.
     * @throws NullPointerException if <tt>c</tt> or any element within it
     * is <tt>null</tt>
     */
    public PriorityQueue(Collection<? extends E> c) {
        initializeArray(c);
        if (c instanceof SortedSet<? extends E>) {
            SortedSet<? extends E> s = (SortedSet<? extends E>) c;
            comparator = (Comparator<? super E>)s.comparator();
            fillFromSorted(s);
        }
        else if (c instanceof PriorityQueue<? extends E>) {
            PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
            comparator = (Comparator<? super E>)s.comparator();
            fillFromSorted(s);
        }
        else {
            comparator = null;
            fillFromUnsorted(c);
        }
    }

    /**
     * Creates a <tt>PriorityQueue</tt> containing the elements in the
     * specified collection.  The priority queue has an initial
     * capacity of 110% of the size of the specified collection or 1
     * if the collection is empty.  This priority queue will be sorted
     * according to the same comparator as the given collection, or
     * according to its elements' natural order if the collection is
     * sorted according to its elements' natural order.
     *
     * @param c the collection whose elements are to be placed
     *        into this priority queue.
     * @throws ClassCastException if elements of the specified collection
     *         cannot be compared to one another according to the priority
     *         queue's ordering.
     * @throws NullPointerException if <tt>c</tt> or any element within it
     * is <tt>null</tt>
     */
    public PriorityQueue(PriorityQueue<? extends E> c) {
        initializeArray(c);
        comparator = (Comparator<? super E>)c.comparator();
        fillFromSorted(c);
    }

    /**
     * Creates a <tt>PriorityQueue</tt> containing the elements in the
     * specified collection.  The priority queue has an initial
     * capacity of 110% of the size of the specified collection or 1
     * if the collection is empty.  This priority queue will be sorted
     * according to the same comparator as the given collection, or
     * according to its elements' natural order if the collection is
     * sorted according to its elements' natural order.
     *
     * @param c the collection whose elements are to be placed
     *        into this priority queue.
     * @throws ClassCastException if elements of the specified collection
     *         cannot be compared to one another according to the priority
     *         queue's ordering.
     * @throws NullPointerException if <tt>c</tt> or any element within it
     * is <tt>null</tt>
     */
    public PriorityQueue(SortedSet<? extends E> c) {
        initializeArray(c);
        comparator = (Comparator<? super E>)c.comparator();
        fillFromSorted(c);
    }

    /**
     * Resize array, if necessary, to be able to hold given index
     */
    private void grow(int index) {
        int newlen = queue.length;
        if (index < newlen) // don't need to grow
            return;
        if (index == Integer.MAX_VALUE)
            throw new OutOfMemoryError();
        while (newlen <= index) {
            if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
                newlen = Integer.MAX_VALUE;
            else
                newlen <<= 2;
        }
        Object[] newQueue = new Object[newlen];
        System.arraycopy(queue, 0, newQueue, 0, queue.length);
        queue = newQueue;
    }
            
    // Queue Methods

    /**
     * Add the specified element to this priority queue.
     *
     * @return <tt>true</tt>
     * @throws ClassCastException if the specified element cannot be compared
     * with elements currently in the priority queue according
     * to the priority queue's ordering.
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     */
    public boolean offer(E o) {
        if (o == null)
            throw new NullPointerException();
        modCount++;
        ++size;

        // Grow backing store if necessary
        if (size >= queue.length) 
            grow(size);

        queue[size] = o;
        fixUp(size);
        return true;
    }

    public E poll() {
        if (size == 0)
            return null;
        return (E) remove(1);
    }

    public E peek() {
        return (E) queue[1];
    }

    // Collection Methods

    // these first two override just to get the throws docs

    /**
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     * @throws ClassCastException if the specified element cannot be compared
     * with elements currently in the priority queue according
     * to the priority queue's ordering.
     */
    public boolean add(E o) {
        return super.add(o);
    }

    /**
     * @throws ClassCastException if any element cannot be compared
     * with elements currently in the priority queue according
     * to the priority queue's ordering.
     * @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
     * is <tt>null</tt>
     */
    public boolean addAll(Collection<? extends E> c) {
        return super.addAll(c);
    }

    public boolean remove(Object o) {
        if (o == null)
            return false;

        if (comparator == null) {
            for (int i = 1; i <= size; i++) {
                if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
                    remove(i);
                    return true;
                }
            }
        } else {
            for (int i = 1; i <= size; i++) {
                if (comparator.compare((E)queue[i], (E)o) == 0) {
                    remove(i);
                    return true;
                }
            }
        }
        return false;
    }

    public Iterator<E> iterator() {
        return new Itr();
    }

    private class Itr implements Iterator<E> {
        /**
         * Index (into queue array) of element to be returned by
         * subsequent call to next.
         */
        private int cursor = 1;

        /**
         * Index of element returned by most recent call to next or
         * previous.  Reset to 0 if this element is deleted by a call
         * to remove.
         */
        private int lastRet = 0;

        /**
         * The modCount value that the iterator believes that the backing
         * List should have.  If this expectation is violated, the iterator
         * has detected concurrent modification.
         */
        private int expectedModCount = modCount;

        public boolean hasNext() {
            return cursor <= size;
        }

        public E next() {
            checkForComodification();
            if (cursor > size)
                throw new NoSuchElementException();
            E result = (E) queue[cursor];
            lastRet = cursor++;
            return result;
        }

        public void remove() {
            if (lastRet == 0)
                throw new IllegalStateException();
            checkForComodification();

            PriorityQueue.this.remove(lastRet);
            if (lastRet < cursor)
                cursor--;
            lastRet = 0;
            expectedModCount = modCount;
        }

        final void checkForComodification() {
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
        }
    }

    /**
     * Returns the number of elements in this priority queue.
     *
     * @return the number of elements in this priority queue.
     */
    public int size() {
        return size;
    }

    /**
     * Remove all elements from the priority queue.
     */
    public void clear() {
        modCount++;

        // Null out element references to prevent memory leak
        for (int i=1; i<=size; i++)
            queue[i] = null;

        size = 0;
    }

    /**
     * Removes and returns the ith element from queue.  Recall
     * that queue is one-based, so 1 <= i <= size.
     *
     * XXX: Could further special-case i==size, but is it worth it?
     * XXX: Could special-case i==0, but is it worth it?
     */
    private E remove(int i) {
        assert i <= size;
        modCount++;

        E result = (E) queue[i];
        queue[i] = queue[size];
        queue[size--] = null;  // Drop extra ref to prevent memory leak
        if (i <= size)
            fixDown(i);
        return result;
    }

    /**
     * Establishes the heap invariant (described above) assuming the heap
     * satisfies the invariant except possibly for the leaf-node indexed by k
     * (which may have a nextExecutionTime less than its parent's).
     *
     * This method functions by "promoting" queue[k] up the hierarchy
     * (by swapping it with its parent) repeatedly until queue[k]
     * is greater than or equal to its parent.
     */
    private void fixUp(int k) {
        if (comparator == null) {
            while (k > 1) {
                int j = k >> 1;
                if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
                    break;
                Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
                k = j;
            }
        } else {
            while (k > 1) {
                int j = k >> 1;
                if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
                    break;
                Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
                k = j;
            }
        }
    }

    /**
     * Establishes the heap invariant (described above) in the subtree
     * rooted at k, which is assumed to satisfy the heap invariant except
     * possibly for node k itself (which may be greater than its children).
     *
     * This method functions by "demoting" queue[k] down the hierarchy
     * (by swapping it with its smaller child) repeatedly until queue[k]
     * is less than or equal to its children.
     */
    private void fixDown(int k) {
        int j;
        if (comparator == null) {
            while ((j = k << 1) <= size) {
                if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
                    j++; // j indexes smallest kid
                if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
                    break;
                Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
                k = j;
            }
        } else {
            while ((j = k << 1) <= size) {
                if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
                    j++; // j indexes smallest kid
                if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
                    break;
                Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
                k = j;
            }
        }
    }

    public Comparator<? super E> comparator() {
        return comparator;
    }

    /**
     * Save the state of the instance to a stream (that
     * is, serialize it).
     *
     * @serialData The length of the array backing the instance is
     * emitted (int), followed by all of its elements (each an
     * <tt>Object</tt>) in the proper order.
     * @param s the stream
     */
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException{
        // Write out element count, and any hidden stuff
        s.defaultWriteObject();

        // Write out array length
        s.writeInt(queue.length);

        // Write out all elements in the proper order.
        for (int i=0; i<size; i++)
            s.writeObject(queue[i]);
    }

    /**
     * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
     * deserialize it).
     * @param s the stream
     */
    private void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException {
        // Read in size, and any hidden stuff
        s.defaultReadObject();

        // Read in array length and allocate array
        int arrayLength = s.readInt();
        queue = new Object[arrayLength];

        // Read in all elements in the proper order.
        for (int i=0; i<size; i++)
            queue[i] = s.readObject();
    }

}

Revision:	1.22
Committed:	Tue Aug 5 12:11:08 2003 UTC (20 years, 9 months ago) by dl
Branch:	MAIN
Changes since 1.21:	+128 -32 lines
Log Message:	Remove Sorted interface, adjust PQ and PBQ
#	User	Rev	Content
1	tim	1.2	package java.util;
2	tim	1.1
3			/**
4	dholmes	1.20	* An unbounded priority queue based on a priority heap. This queue orders
5	brian	1.6	* elements according to an order specified at construction time, which is
6	tim	1.19	* specified in the same manner as {@link java.util.TreeSet} and
7	dholmes	1.18	* {@link java.util.TreeMap}: elements are ordered
8	tim	1.2	* either according to their <i>natural order</i> (see {@link Comparable}), or
9	tim	1.19	* according to a {@link java.util.Comparator}, depending on which
10	dholmes	1.18	* constructor is used.
11	tim	1.19	* <p>The <em>head</em> of this queue is the <em>least</em> element with
12			* respect to the specified ordering.
13	dholmes	1.18	* If multiple elements are tied for least value, the
14	tim	1.14	* head is one of those elements. A priority queue does not permit
15	dholmes	1.11	* <tt>null</tt> elements.
16	tim	1.14	*
17	dholmes	1.11	* <p>The {@link #remove()} and {@link #poll()} methods remove and
18			* return the head of the queue.
19			*
20			* <p>The {@link #element()} and {@link #peek()} methods return, but do
21			* not delete, the head of the queue.
22	tim	1.2	*
23	dl	1.7	* <p>A priority queue has a <i>capacity</i>. The capacity is the
24			* size of the array used internally to store the elements on the
25	dholmes	1.20	* queue.
26	dholmes	1.18	* It is always at least as large as the queue size. As
27	dl	1.7	* elements are added to a priority queue, its capacity grows
28			* automatically. The details of the growth policy are not specified.
29	tim	1.2	*
30	dholmes	1.11	* <p>Implementation note: this implementation provides O(log(n)) time
31			* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
32			* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
33			* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
34			* constant time for the retrieval methods (<tt>peek</tt>,
35			* <tt>element</tt>, and <tt>size</tt>).
36	tim	1.2	*
37			* <p>This class is a member of the
38			* <a href="{@docRoot}/../guide/collections/index.html">
39			* Java Collections Framework</a>.
40	dl	1.7	* @since 1.5
41			* @author Josh Bloch
42	tim	1.2	*/
43			public class PriorityQueue<E> extends AbstractQueue<E>
44	dl	1.22	implements Queue<E>, java.io.Serializable {
45	dholmes	1.11
46	tim	1.2	private static final int DEFAULT_INITIAL_CAPACITY = 11;
47	tim	1.1
48	tim	1.2	/**
49			* Priority queue represented as a balanced binary heap: the two children
50			* of queue[n] are queue[2n] and queue[2n + 1]. The priority queue is
51			* ordered by comparator, or by the elements' natural ordering, if
52	brian	1.6	* comparator is null: For each node n in the heap and each descendant d
53			* of n, n <= d.
54	tim	1.2	*
55	brian	1.6	* The element with the lowest value is in queue[1], assuming the queue is
56			* nonempty. (A one-based array is used in preference to the traditional
57			* zero-based array to simplify parent and child calculations.)
58	tim	1.2	*
59			* queue.length must be >= 2, even if size == 0.
60			*/
61	tim	1.16	private transient Object[] queue;
62	tim	1.1
63	tim	1.2	/**
64			* The number of elements in the priority queue.
65			*/
66			private int size = 0;
67	tim	1.1
68	tim	1.2	/**
69			* The comparator, or null if priority queue uses elements'
70			* natural ordering.
71			*/
72	tim	1.16	private final Comparator<? super E> comparator;
73	tim	1.2
74			/**
75			* The number of times this priority queue has been
76			* <i>structurally modified</i>. See AbstractList for gory details.
77			*/
78	dl	1.5	private transient int modCount = 0;
79	tim	1.2
80			/**
81	dholmes	1.21	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
82	dl	1.7	* (11) that orders its elements according to their natural
83			* ordering (using <tt>Comparable</tt>.)
84	tim	1.2	*/
85			public PriorityQueue() {
86	dholmes	1.11	this(DEFAULT_INITIAL_CAPACITY, null);
87	tim	1.1	}
88	tim	1.2
89			/**
90	dholmes	1.21	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
91	dl	1.7	* that orders its elements according to their natural ordering
92			* (using <tt>Comparable</tt>.)
93	tim	1.2	*
94			* @param initialCapacity the initial capacity for this priority queue.
95			*/
96			public PriorityQueue(int initialCapacity) {
97			this(initialCapacity, null);
98	tim	1.1	}
99	tim	1.2
100			/**
101	dholmes	1.21	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
102	tim	1.2	* that orders its elements according to the specified comparator.
103			*
104			* @param initialCapacity the initial capacity for this priority queue.
105			* @param comparator the comparator used to order this priority queue.
106	dholmes	1.11	* If <tt>null</tt> then the order depends on the elements' natural
107			* ordering.
108	dholmes	1.15	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
109			* than 1
110	tim	1.2	*/
111	tim	1.16	public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
112	tim	1.2	if (initialCapacity < 1)
113	dholmes	1.15	throw new IllegalArgumentException();
114	tim	1.16	this.queue = new Object[initialCapacity + 1];
115	tim	1.2	this.comparator = comparator;
116	tim	1.1	}
117
118	tim	1.2	/**
119	dl	1.22	* Common code to initialize underlying queue array across
120			* constructors below.
121			*/
122			private void initializeArray(Collection<? extends E> c) {
123			int sz = c.size();
124			int initialCapacity = (int)Math.min((sz * 110L) / 100,
125			Integer.MAX_VALUE - 1);
126			if (initialCapacity < 1)
127			initialCapacity = 1;
128
129			this.queue = new Object[initialCapacity + 1];
130			}
131
132			/**
133			* Initially fill elements of the queue array under the
134			* knowledge that it is sorted or is another PQ, in which
135			* case we can just place the elements without fixups.
136			*/
137			private void fillFromSorted(Collection<? extends E> c) {
138			for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
139			queue[++size] = i.next();
140			}
141
142
143			/**
144			* Initially fill elements of the queue array that is
145			* not to our knowledge sorted, so we must add them
146			* one by one.
147			*/
148			private void fillFromUnsorted(Collection<? extends E> c) {
149			for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
150			add(i.next());
151			}
152
153			/**
154			* Creates a <tt>PriorityQueue</tt> containing the elements in the
155			* specified collection. The priority queue has an initial
156			* capacity of 110% of the size of the specified collection or 1
157			* if the collection is empty. If the specified collection is an
158			* instance of a {@link SortedSet} or is another
159			* <tt>PriorityQueue</tt>, the priority queue will be sorted
160			* according to the same comparator, or according to its elements'
161			* natural order if the collection is sorted according to its
162			* elements' natural order. Otherwise, the priority queue is
163			* ordered according to its elements' natural order.
164	tim	1.2	*
165	dholmes	1.15	* @param c the collection whose elements are to be placed
166	tim	1.2	* into this priority queue.
167			* @throws ClassCastException if elements of the specified collection
168			* cannot be compared to one another according to the priority
169			* queue's ordering.
170	dholmes	1.15	* @throws NullPointerException if <tt>c</tt> or any element within it
171			* is <tt>null</tt>
172	tim	1.2	*/
173	tim	1.16	public PriorityQueue(Collection<? extends E> c) {
174	dl	1.22	initializeArray(c);
175			if (c instanceof SortedSet<? extends E>) {
176			SortedSet<? extends E> s = (SortedSet<? extends E>) c;
177			comparator = (Comparator<? super E>)s.comparator();
178			fillFromSorted(s);
179			}
180			else if (c instanceof PriorityQueue<? extends E>) {
181			PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
182			comparator = (Comparator<? super E>)s.comparator();
183			fillFromSorted(s);
184			}
185			else {
186	tim	1.2	comparator = null;
187	dl	1.22	fillFromUnsorted(c);
188	tim	1.2	}
189	dl	1.22	}
190
191			/**
192			* Creates a <tt>PriorityQueue</tt> containing the elements in the
193			* specified collection. The priority queue has an initial
194			* capacity of 110% of the size of the specified collection or 1
195			* if the collection is empty. This priority queue will be sorted
196			* according to the same comparator as the given collection, or
197			* according to its elements' natural order if the collection is
198			* sorted according to its elements' natural order.
199			*
200			* @param c the collection whose elements are to be placed
201			* into this priority queue.
202			* @throws ClassCastException if elements of the specified collection
203			* cannot be compared to one another according to the priority
204			* queue's ordering.
205			* @throws NullPointerException if <tt>c</tt> or any element within it
206			* is <tt>null</tt>
207			*/
208			public PriorityQueue(PriorityQueue<? extends E> c) {
209			initializeArray(c);
210			comparator = (Comparator<? super E>)c.comparator();
211			fillFromSorted(c);
212			}
213	dholmes	1.18
214	dl	1.22	/**
215			* Creates a <tt>PriorityQueue</tt> containing the elements in the
216			* specified collection. The priority queue has an initial
217			* capacity of 110% of the size of the specified collection or 1
218			* if the collection is empty. This priority queue will be sorted
219			* according to the same comparator as the given collection, or
220			* according to its elements' natural order if the collection is
221			* sorted according to its elements' natural order.
222			*
223			* @param c the collection whose elements are to be placed
224			* into this priority queue.
225			* @throws ClassCastException if elements of the specified collection
226			* cannot be compared to one another according to the priority
227			* queue's ordering.
228			* @throws NullPointerException if <tt>c</tt> or any element within it
229			* is <tt>null</tt>
230			*/
231			public PriorityQueue(SortedSet<? extends E> c) {
232			initializeArray(c);
233			comparator = (Comparator<? super E>)c.comparator();
234			fillFromSorted(c);
235	tim	1.1	}
236
237	dl	1.22	/**
238			* Resize array, if necessary, to be able to hold given index
239			*/
240			private void grow(int index) {
241			int newlen = queue.length;
242			if (index < newlen) // don't need to grow
243			return;
244			if (index == Integer.MAX_VALUE)
245			throw new OutOfMemoryError();
246			while (newlen <= index) {
247			if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow
248			newlen = Integer.MAX_VALUE;
249			else
250			newlen <<= 2;
251			}
252			Object[] newQueue = new Object[newlen];
253			System.arraycopy(queue, 0, newQueue, 0, queue.length);
254			queue = newQueue;
255			}
256
257	tim	1.2	// Queue Methods
258
259			/**
260	dholmes	1.11	* Add the specified element to this priority queue.
261	tim	1.2	*
262	dholmes	1.11	* @return <tt>true</tt>
263			* @throws ClassCastException if the specified element cannot be compared
264			* with elements currently in the priority queue according
265			* to the priority queue's ordering.
266	dholmes	1.18	* @throws NullPointerException if the specified element is <tt>null</tt>.
267	tim	1.2	*/
268	dholmes	1.18	public boolean offer(E o) {
269			if (o == null)
270	dholmes	1.11	throw new NullPointerException();
271			modCount++;
272			++size;
273
274			// Grow backing store if necessary
275	dl	1.22	if (size >= queue.length)
276			grow(size);
277	dholmes	1.11
278	dholmes	1.18	queue[size] = o;
279	dholmes	1.11	fixUp(size);
280			return true;
281			}
282
283	tim	1.1	public E poll() {
284	tim	1.2	if (size == 0)
285			return null;
286	tim	1.16	return (E) remove(1);
287	tim	1.1	}
288	tim	1.2
289	tim	1.1	public E peek() {
290	tim	1.16	return (E) queue[1];
291	tim	1.1	}
292
293	tim	1.2	// Collection Methods
294
295	dholmes	1.11	// these first two override just to get the throws docs
296
297			/**
298			* @throws NullPointerException if the specified element is <tt>null</tt>.
299	dholmes	1.15	* @throws ClassCastException if the specified element cannot be compared
300			* with elements currently in the priority queue according
301			* to the priority queue's ordering.
302	dholmes	1.11	*/
303	dholmes	1.18	public boolean add(E o) {
304			return super.add(o);
305	dholmes	1.11	}
306
307	tim	1.14	/**
308	dholmes	1.15	* @throws ClassCastException if any element cannot be compared
309			* with elements currently in the priority queue according
310			* to the priority queue's ordering.
311	dholmes	1.18	* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
312			* is <tt>null</tt>
313	tim	1.14	*/
314			public boolean addAll(Collection<? extends E> c) {
315			return super.addAll(c);
316			}
317	dholmes	1.11
318	dl	1.12	public boolean remove(Object o) {
319	dholmes	1.11	if (o == null)
320	dholmes	1.15	return false;
321	tim	1.2
322			if (comparator == null) {
323			for (int i = 1; i <= size; i++) {
324	tim	1.16	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
325	tim	1.2	remove(i);
326			return true;
327			}
328			}
329			} else {
330			for (int i = 1; i <= size; i++) {
331	tim	1.16	if (comparator.compare((E)queue[i], (E)o) == 0) {
332	tim	1.2	remove(i);
333			return true;
334			}
335			}
336			}
337	tim	1.1	return false;
338			}
339	tim	1.2
340			public Iterator<E> iterator() {
341	dl	1.7	return new Itr();
342	tim	1.2	}
343
344			private class Itr implements Iterator<E> {
345	dl	1.7	/**
346			* Index (into queue array) of element to be returned by
347	tim	1.2	* subsequent call to next.
348	dl	1.7	*/
349			private int cursor = 1;
350	tim	1.2
351	dl	1.7	/**
352			* Index of element returned by most recent call to next or
353			* previous. Reset to 0 if this element is deleted by a call
354			* to remove.
355			*/
356			private int lastRet = 0;
357
358			/**
359			* The modCount value that the iterator believes that the backing
360			* List should have. If this expectation is violated, the iterator
361			* has detected concurrent modification.
362			*/
363			private int expectedModCount = modCount;
364	tim	1.2
365	dl	1.7	public boolean hasNext() {
366			return cursor <= size;
367			}
368
369			public E next() {
370	tim	1.2	checkForComodification();
371			if (cursor > size)
372	dl	1.7	throw new NoSuchElementException();
373	tim	1.16	E result = (E) queue[cursor];
374	tim	1.2	lastRet = cursor++;
375			return result;
376	dl	1.7	}
377	tim	1.2
378	dl	1.7	public void remove() {
379			if (lastRet == 0)
380			throw new IllegalStateException();
381	tim	1.2	checkForComodification();
382
383			PriorityQueue.this.remove(lastRet);
384			if (lastRet < cursor)
385			cursor--;
386			lastRet = 0;
387			expectedModCount = modCount;
388	dl	1.7	}
389	tim	1.2
390	dl	1.7	final void checkForComodification() {
391			if (modCount != expectedModCount)
392			throw new ConcurrentModificationException();
393			}
394	tim	1.2	}
395
396			/**
397			* Returns the number of elements in this priority queue.
398	tim	1.10	*
399	tim	1.2	* @return the number of elements in this priority queue.
400			*/
401	tim	1.1	public int size() {
402	tim	1.2	return size;
403	tim	1.1	}
404	tim	1.2
405			/**
406			* Remove all elements from the priority queue.
407			*/
408			public void clear() {
409			modCount++;
410
411			// Null out element references to prevent memory leak
412			for (int i=1; i<=size; i++)
413			queue[i] = null;
414
415			size = 0;
416			}
417
418			/**
419			* Removes and returns the ith element from queue. Recall
420			* that queue is one-based, so 1 <= i <= size.
421			*
422			* XXX: Could further special-case i==size, but is it worth it?
423			* XXX: Could special-case i==0, but is it worth it?
424			*/
425			private E remove(int i) {
426			assert i <= size;
427			modCount++;
428
429	tim	1.16	E result = (E) queue[i];
430	tim	1.2	queue[i] = queue[size];
431			queue[size--] = null; // Drop extra ref to prevent memory leak
432			if (i <= size)
433			fixDown(i);
434			return result;
435	tim	1.1	}
436
437	tim	1.2	/**
438			* Establishes the heap invariant (described above) assuming the heap
439			* satisfies the invariant except possibly for the leaf-node indexed by k
440			* (which may have a nextExecutionTime less than its parent's).
441			*
442			* This method functions by "promoting" queue[k] up the hierarchy
443			* (by swapping it with its parent) repeatedly until queue[k]
444			* is greater than or equal to its parent.
445			*/
446			private void fixUp(int k) {
447			if (comparator == null) {
448			while (k > 1) {
449			int j = k >> 1;
450	tim	1.16	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
451	tim	1.2	break;
452	tim	1.16	Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
453	tim	1.2	k = j;
454			}
455			} else {
456			while (k > 1) {
457			int j = k >> 1;
458	tim	1.16	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
459	tim	1.2	break;
460	tim	1.16	Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
461	tim	1.2	k = j;
462			}
463			}
464			}
465
466			/**
467			* Establishes the heap invariant (described above) in the subtree
468			* rooted at k, which is assumed to satisfy the heap invariant except
469			* possibly for node k itself (which may be greater than its children).
470			*
471			* This method functions by "demoting" queue[k] down the hierarchy
472			* (by swapping it with its smaller child) repeatedly until queue[k]
473			* is less than or equal to its children.
474			*/
475			private void fixDown(int k) {
476			int j;
477			if (comparator == null) {
478			while ((j = k << 1) <= size) {
479	tim	1.16	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
480	tim	1.2	j++; // j indexes smallest kid
481	tim	1.16	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
482	tim	1.2	break;
483	tim	1.16	Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
484	tim	1.2	k = j;
485			}
486			} else {
487			while ((j = k << 1) <= size) {
488	tim	1.16	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
489	tim	1.2	j++; // j indexes smallest kid
490	tim	1.16	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
491	tim	1.2	break;
492	tim	1.16	Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
493	tim	1.2	k = j;
494			}
495			}
496			}
497
498	tim	1.16	public Comparator<? super E> comparator() {
499	tim	1.2	return comparator;
500			}
501	dl	1.5
502			/**
503			* Save the state of the instance to a stream (that
504			* is, serialize it).
505			*
506			* @serialData The length of the array backing the instance is
507			* emitted (int), followed by all of its elements (each an
508			* <tt>Object</tt>) in the proper order.
509	dl	1.7	* @param s the stream
510	dl	1.5	*/
511	dl	1.22	private void writeObject(java.io.ObjectOutputStream s)
512	dl	1.5	throws java.io.IOException{
513	dl	1.7	// Write out element count, and any hidden stuff
514			s.defaultWriteObject();
515	dl	1.5
516			// Write out array length
517			s.writeInt(queue.length);
518
519	dl	1.7	// Write out all elements in the proper order.
520			for (int i=0; i<size; i++)
521	dl	1.5	s.writeObject(queue[i]);
522			}
523
524			/**
525			* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
526			* deserialize it).
527	dl	1.7	* @param s the stream
528	dl	1.5	*/
529	dl	1.22	private void readObject(java.io.ObjectInputStream s)
530	dl	1.5	throws java.io.IOException, ClassNotFoundException {
531	dl	1.7	// Read in size, and any hidden stuff
532			s.defaultReadObject();
533	dl	1.5
534			// Read in array length and allocate array
535			int arrayLength = s.readInt();
536	tim	1.16	queue = new Object[arrayLength];
537	dl	1.5
538	dl	1.7	// Read in all elements in the proper order.
539			for (int i=0; i<size; i++)
540	tim	1.16	queue[i] = s.readObject();
541	dl	1.5	}
542
543	tim	1.1	}
544	dholmes	1.11