--- jsr166/src/main/java/util/PriorityQueue.java 2005/11/29 08:52:26 1.59
+++ jsr166/src/main/java/util/PriorityQueue.java 2007/01/07 07:38:27 1.66
@@ -1,28 +1,27 @@
/*
* %W% %E%
*
- * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
+ * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
-import java.util.*; // for javadoc (till 6280605 is fixed)
/**
- * An unbounded priority {@linkplain Queue queue} based on a priority
- * heap. The elements of the priority queue are ordered according to
- * their {@linkplain Comparable natural ordering}, or by a {@link
- * Comparator} provided at queue construction time, depending on which
- * constructor is used. A priority queue does not permit
- * null elements. A priority queue relying on natural
- * ordering also does not permit insertion of non-comparable objects
- * (doing so may result in ClassCastException).
+ * An unbounded priority {@linkplain Queue queue} based on a priority heap.
+ * The elements of the priority queue are ordered according to their
+ * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
+ * provided at queue construction time, depending on which constructor is
+ * used. A priority queue does not permit {@code null} elements.
+ * A priority queue relying on natural ordering also does not permit
+ * insertion of non-comparable objects (doing so may result in
+ * {@code ClassCastException}).
*
*
The head of this queue is the least element
* with respect to the specified ordering. If multiple elements are
* tied for least value, the head is one of those elements -- ties are
- * broken arbitrarily. The queue retrieval operations poll,
- * remove, peek, and element access the
+ * broken arbitrarily. The queue retrieval operations {@code poll},
+ * {@code remove}, {@code peek}, and {@code element} access the
* element at the head of the queue.
*
*
A priority queue is unbounded, but has an internal
@@ -37,27 +36,28 @@ import java.util.*; // for javadoc (till
* Iterator} interfaces. The Iterator provided in method {@link
* #iterator()} is not guaranteed to traverse the elements of
* the priority queue in any particular order. If you need ordered
- * traversal, consider using Arrays.sort(pq.toArray()).
+ * traversal, consider using {@code Arrays.sort(pq.toArray())}.
*
*
Note that this implementation is not synchronized.
- * Multiple threads should not access a PriorityQueue
- * instance concurrently if any of the threads modifies the list
- * structurally. Instead, use the thread-safe {@link
+ * Multiple threads should not access a {@code PriorityQueue}
+ * instance concurrently if any of the threads modifies the queue.
+ * Instead, use the thread-safe {@link
* java.util.concurrent.PriorityBlockingQueue} class.
*
- *
Implementation note: this implementation provides O(log(n)) time
- * for the insertion methods (offer, poll,
- * remove() and add) methods; linear time for the
- * remove(Object) and contains(Object) methods; and
- * constant time for the retrieval methods (peek,
- * element, and size).
+ *
Implementation note: this implementation provides
+ * O(log(n)) time for the enqueing and dequeing methods
+ * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
+ * linear time for the {@code remove(Object)} and {@code contains(Object)}
+ * methods; and constant time for the retrieval methods
+ * ({@code peek}, {@code element}, and {@code size}).
*
*
This class is a member of the
- *
+ *
* Java Collections Framework.
+ *
* @since 1.5
- * @version 1.8, 08/27/05
- * @author Josh Bloch
+ * @version %I%, %G%
+ * @author Josh Bloch, Doug Lea
* @param the type of elements held in this collection
*/
public class PriorityQueue extends AbstractQueue
@@ -95,7 +95,7 @@ public class PriorityQueue extends Ab
private transient int modCount = 0;
/**
- * Creates a PriorityQueue with the default initial
+ * Creates a {@code PriorityQueue} with the default initial
* capacity (11) that orders its elements according to their
* {@linkplain Comparable natural ordering}.
*/
@@ -104,27 +104,27 @@ public class PriorityQueue extends Ab
}
/**
- * Creates a PriorityQueue with the specified initial
+ * Creates a {@code PriorityQueue} with the specified initial
* capacity that orders its elements according to their
* {@linkplain Comparable natural ordering}.
*
* @param initialCapacity the initial capacity for this priority queue
- * @throws IllegalArgumentException if initialCapacity is less
- * than 1
+ * @throws IllegalArgumentException if {@code initialCapacity} is less
+ * than 1
*/
public PriorityQueue(int initialCapacity) {
this(initialCapacity, null);
}
/**
- * Creates a PriorityQueue with the specified initial capacity
+ * Creates a {@code PriorityQueue} 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 that will be used to order
- * this priority queue. If null, the natural
- * ordering of the elements will be used.
- * @throws IllegalArgumentException if initialCapacity is
+ * @param comparator the comparator that will be used to order this
+ * priority queue. If {@code null}, the {@linkplain Comparable
+ * natural ordering} of the elements will be used.
+ * @throws IllegalArgumentException if {@code initialCapacity} is
* less than 1
*/
public PriorityQueue(int initialCapacity,
@@ -138,12 +138,12 @@ public class PriorityQueue extends Ab
}
/**
- * Creates a PriorityQueue containing the elements in the
- * specified collection. If the specified collection is an
- * instance of a {@link java.util.SortedSet} or is another
- * PriorityQueue, the priority queue will be ordered
- * according to the same ordering. Otherwise, this priority queue
- * will be ordered according to the natural ordering of its elements.
+ * Creates a {@code PriorityQueue} containing the elements in the
+ * specified collection. If the specified collection is an instance of
+ * a {@link SortedSet} or is another {@code PriorityQueue}, this
+ * priority queue will be ordered according to the same ordering.
+ * Otherwise, this priority queue will be ordered according to the
+ * {@linkplain Comparable natural ordering} of its elements.
*
* @param c the collection whose elements are to be placed
* into this priority queue
@@ -168,15 +168,15 @@ public class PriorityQueue extends Ab
}
/**
- * Creates a PriorityQueue containing the elements in the
+ * Creates a {@code PriorityQueue} containing the elements in the
* specified priority queue. This priority queue will be
* ordered according to the same ordering as the given priority
* queue.
*
* @param c the priority queue whose elements are to be placed
* into this priority queue
- * @throws ClassCastException if elements of c cannot be
- * compared to one another according to c's
+ * @throws ClassCastException if elements of {@code c} cannot be
+ * compared to one another according to {@code c}'s
* ordering
* @throws NullPointerException if the specified priority queue or any
* of its elements are null
@@ -187,12 +187,12 @@ public class PriorityQueue extends Ab
}
/**
- * Creates a PriorityQueue containing the elements in the
- * specified sorted set. This priority queue will be ordered
+ * Creates a {@code PriorityQueue} containing the elements in the
+ * specified sorted set. This priority queue will be ordered
* according to the same ordering as the given sorted set.
*
* @param c the sorted set whose elements are to be placed
- * into this priority queue.
+ * into this priority queue
* @throws ClassCastException if elements of the specified sorted
* set cannot be compared to one another according to the
* sorted set's ordering
@@ -205,7 +205,8 @@ public class PriorityQueue extends Ab
}
/**
- * Initialize queue array with elements from the given Collection.
+ * Initializes queue array with elements from the given Collection.
+ *
* @param c the collection
*/
private void initFromCollection(Collection extends E> c) {
@@ -240,7 +241,7 @@ public class PriorityQueue extends Ab
/**
* Inserts the specified element into this priority queue.
*
- * @return true (as specified by {@link Collection#add})
+ * @return {@code true} (as specified by {@link Collection#add})
* @throws ClassCastException if the specified element cannot be
* compared with elements currently in this priority queue
* according to the priority queue's ordering
@@ -253,7 +254,7 @@ public class PriorityQueue extends Ab
/**
* Inserts the specified element into this priority queue.
*
- * @return true (as specified by {@link Queue#offer})
+ * @return {@code true} (as specified by {@link Queue#offer})
* @throws ClassCastException if the specified element cannot be
* compared with elements currently in this priority queue
* according to the priority queue's ordering
@@ -291,13 +292,14 @@ public class PriorityQueue extends Ab
/**
* Removes a single instance of the specified element from this queue,
- * if it is present. More formally, removes an element e such
- * that o.equals(e), if this queue contains one or more such
- * elements. Returns true if this queue contained the specified element
- * (or equivalently, if this queue changed as a result of the call).
+ * if it is present. More formally, removes an element {@code e} such
+ * that {@code o.equals(e)}, if this queue contains one or more such
+ * elements. Returns {@code true} if and only if this queue contained
+ * the specified element (or equivalently, if this queue changed as a
+ * result of the call).
*
* @param o element to be removed from this queue, if present
- * @return true if this queue changed as a result of the call
+ * @return {@code true} if this queue changed as a result of the call
*/
public boolean remove(Object o) {
int i = indexOf(o);
@@ -314,7 +316,7 @@ public class PriorityQueue extends Ab
* Needed by iterator.remove.
*
* @param o element to be removed from this queue, if present
- * @return true if removed
+ * @return {@code true} if removed
*/
boolean removeEq(Object o) {
for (int i = 0; i < size; i++) {
@@ -327,25 +329,28 @@ public class PriorityQueue extends Ab
}
/**
- * Returns true if this queue contains the specified element.
- * More formally, returns true if and only if this queue contains
- * at least one element e such that o.equals(e).
+ * Returns {@code true} if this queue contains the specified element.
+ * More formally, returns {@code true} if and only if this queue contains
+ * at least one element {@code e} such that {@code o.equals(e)}.
*
* @param o object to be checked for containment in this queue
- * @return true if this queue contains the specified element
+ * @return {@code true} if this queue contains the specified element
*/
public boolean contains(Object o) {
return indexOf(o) != -1;
}
/**
- * Returns an array containing all of the elements in this queue,
+ * Returns an array containing all of the elements in this queue.
* The elements are in no particular order.
*
* The returned array will be "safe" in that no references to it are
- * maintained by this list. (In other words, this method must allocate
+ * maintained by this queue. (In other words, this method must allocate
* a new array). The caller is thus free to modify the returned array.
*
+ *
This method acts as bridge between array-based and collection-based
+ * APIs.
+ *
* @return an array containing all of the elements in this queue
*/
public Object[] toArray() {
@@ -353,24 +358,37 @@ public class PriorityQueue extends Ab
}
/**
- * Returns an array containing all of the elements in this queue.
- * The elements are in no particular order. The runtime type of
- * the returned array is that of the specified array. If the queue
- * 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 queue.
+ * Returns an array containing all of the elements in this queue; the
+ * runtime type of the returned array is that of the specified array.
+ * The returned array elements are in no particular order.
+ * If the queue 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 queue.
*
* If the queue fits in the specified array with room to spare
* (i.e., the array has more elements than the queue), the element in
* the array immediately following the end of the collection is set to
- * null. (This is useful in determining the length of the
- * queue only if the caller knows that the queue does not contain
- * any null elements.)
+ * {@code null}.
+ *
+ *
Like the {@link #toArray()} method, this method acts as bridge between
+ * array-based and collection-based APIs. Further, this method allows
+ * precise control over the runtime type of the output array, and may,
+ * under certain circumstances, be used to save allocation costs.
+ *
+ *
Suppose x is a queue known to contain only strings.
+ * The following code can be used to dump the queue into a newly
+ * allocated array of String:
+ *
+ *
+ * String[] y = x.toArray(new String[0]);
+ *
+ * Note that toArray(new Object[0]) is identical in function to
+ * toArray().
*
* @param a the array into which the elements of the queue are to
* be stored, if it is big enough; otherwise, a new array of the
* same runtime type is allocated for this purpose.
- * @return an array containing the elements of the queue
+ * @return an array containing all of the elements in this queue
* @throws ArrayStoreException if the runtime type of the specified array
* is not a supertype of the runtime type of every element in
* this queue
@@ -419,7 +437,7 @@ public class PriorityQueue extends Ab
* after we've completed the "normal" iteration.
*
* We expect that most iterations, even those involving removals,
- * will not use need to store elements in this field.
+ * will not need to store elements in this field.
*/
private ArrayDeque forgetMeNot = null;
@@ -431,7 +449,7 @@ public class PriorityQueue extends Ab
/**
* The modCount value that the iterator believes that the backing
- * List should have. If this expectation is violated, the iterator
+ * Queue should have. If this expectation is violated, the iterator
* has detected concurrent modification.
*/
private int expectedModCount = modCount;
@@ -458,8 +476,6 @@ public class PriorityQueue extends Ab
public void remove() {
if (expectedModCount != modCount)
throw new ConcurrentModificationException();
- if (lastRet == -1 && lastRetElt == null)
- throw new IllegalStateException();
if (lastRet != -1) {
E moved = PriorityQueue.this.removeAt(lastRet);
lastRet = -1;
@@ -470,13 +486,14 @@ public class PriorityQueue extends Ab
forgetMeNot = new ArrayDeque();
forgetMeNot.add(moved);
}
- } else {
+ } else if (lastRetElt != null) {
PriorityQueue.this.removeEq(lastRetElt);
lastRetElt = null;
- }
+ } else {
+ throw new IllegalStateException();
+ }
expectedModCount = modCount;
}
-
}
public int size() {
@@ -499,8 +516,8 @@ public class PriorityQueue extends Ab
return null;
int s = --size;
modCount++;
- E result = (E)queue[0];
- E x = (E)queue[s];
+ E result = (E) queue[0];
+ E x = (E) queue[s];
queue[s] = null;
if (s != 0)
siftDown(0, x);
@@ -517,7 +534,7 @@ public class PriorityQueue extends Ab
* i. Under these circumstances, this method returns the element
* that was previously at the end of the list and is now at some
* position before i. This fact is used by iterator.remove so as to
- * avoid missing traverseing elements.
+ * avoid missing traversing elements.
*/
private E removeAt(int i) {
assert i >= 0 && i < size;
@@ -562,7 +579,7 @@ public class PriorityQueue extends Ab
while (k > 0) {
int parent = (k - 1) >>> 1;
Object e = queue[parent];
- if (key.compareTo((E)e) >= 0)
+ if (key.compareTo((E) e) >= 0)
break;
queue[k] = e;
k = parent;
@@ -574,7 +591,7 @@ public class PriorityQueue extends Ab
while (k > 0) {
int parent = (k - 1) >>> 1;
Object e = queue[parent];
- if (comparator.compare(x, (E)e) >= 0)
+ if (comparator.compare(x, (E) e) >= 0)
break;
queue[k] = e;
k = parent;
@@ -605,9 +622,9 @@ public class PriorityQueue extends Ab
Object c = queue[child];
int right = child + 1;
if (right < size &&
- ((Comparable super E>)c).compareTo((E)queue[right]) > 0)
+ ((Comparable super E>) c).compareTo((E) queue[right]) > 0)
c = queue[child = right];
- if (key.compareTo((E)c) <= 0)
+ if (key.compareTo((E) c) <= 0)
break;
queue[k] = c;
k = child;
@@ -622,9 +639,9 @@ public class PriorityQueue extends Ab
Object c = queue[child];
int right = child + 1;
if (right < size &&
- comparator.compare((E)c, (E)queue[right]) > 0)
+ comparator.compare((E) c, (E) queue[right]) > 0)
c = queue[child = right];
- if (comparator.compare(x, (E)c) <= 0)
+ if (comparator.compare(x, (E) c) <= 0)
break;
queue[k] = c;
k = child;
@@ -638,29 +655,29 @@ public class PriorityQueue extends Ab
*/
private void heapify() {
for (int i = (size >>> 1) - 1; i >= 0; i--)
- siftDown(i, (E)queue[i]);
+ siftDown(i, (E) queue[i]);
}
/**
* Returns the comparator used to order the elements in this
- * queue, or null if this queue is sorted according to
+ * queue, or {@code null} if this queue is sorted according to
* the {@linkplain Comparable natural ordering} of its elements.
*
* @return the comparator used to order this queue, or
- * null if this queue is sorted according to the
- * natural ordering of its elements.
+ * {@code null} if this queue is sorted according to the
+ * natural ordering of its elements
*/
public Comparator super E> comparator() {
return comparator;
}
/**
- * Save the state of the instance to a stream (that
- * is, serialize it).
+ * Saves the state of the instance to a stream (that
+ * is, serializes it).
*
* @serialData The length of the array backing the instance is
- * emitted (int), followed by all of its elements (each an
- * Object) in the proper order.
+ * emitted (int), followed by all of its elements
+ * (each an {@code Object}) in the proper order.
* @param s the stream
*/
private void writeObject(java.io.ObjectOutputStream s)
@@ -668,18 +685,18 @@ public class PriorityQueue extends Ab
// Write out element count, and any hidden stuff
s.defaultWriteObject();
- // Write out array length
- // For compatibility with 1.5 version, must be at least 2.
- s.writeInt(Math.max(2, queue.length));
+ // Write out array length, for compatibility with 1.5 version
+ s.writeInt(Math.max(2, size + 1));
- // Write out all elements in the proper order.
- for (int i=0; iPriorityQueue instance from a stream
- * (that is, deserialize it).
+ * Reconstitutes the {@code PriorityQueue} instance from a stream
+ * (that is, deserializes it).
+ *
* @param s the stream
*/
private void readObject(java.io.ObjectInputStream s)
@@ -687,13 +704,17 @@ public class PriorityQueue extends Ab
// 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