--- jsr166/src/main/java/util/PriorityQueue.java 2003/05/19 02:45:07 1.4
+++ jsr166/src/main/java/util/PriorityQueue.java 2003/06/23 02:26:15 1.6
@@ -1,33 +1,27 @@
package java.util;
-/*
- * Todo
- *
- * 1) Make it serializable.
- */
-
/**
* An unbounded priority queue based on a priority heap. This queue orders
- * elements according to the order specified at creation time. This order is
- * specified as for {@link TreeSet} and {@link TreeMap}: Elements are ordered
+ * elements according to an order specified at construction time, which is
+ * specified in the same manner as {@link TreeSet} and {@link TreeMap}: elements are ordered
* either according to their natural order (see {@link Comparable}), or
* according to a {@link Comparator}, depending on which constructor is used.
* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the
* minimal element with respect to the specified ordering. If multiple
- * these elements are tied for least value, no guarantees are made as to
- * which of elements is returned.
+ * elements are tied for least value, no guarantees are made as to
+ * which of these elements is returned.
*
- * Each priority queue has a capacity. The capacity is the size of
- * the array used 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 list,
+ *
A priority queue has a capacity. 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.
*
*
Implementation note: this implementation provides O(log(n)) time for
- * the offer, poll, remove() and add
+ * the insertion methods (offer, poll, remove() and add)
* methods; linear time for the remove(Object) and
- * contains methods; and constant time for the peek,
- * element, and size methods.
+ * contains(Object) methods; and constant time for the retrieval methods (peek,
+ * element, and size).
*
*
This class is a member of the
*
@@ -42,16 +36,16 @@ public class PriorityQueue extends Ab
* 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
- * of n, d, n <= d.
+ * 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.
+ * 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 E[] queue;
+ private transient E[] queue;
/**
* The number of elements in the priority queue.
@@ -68,11 +62,11 @@ public class PriorityQueue extends Ab
* The number of times this priority queue has been
* structurally modified. See AbstractList for gory details.
*/
- private int modCount = 0;
+ private transient int modCount = 0;
/**
* Create a new priority queue with the default initial capacity (11)
- * that orders its elements according to their natural ordering.
+ * that orders its elements according to their natural ordering (using Comparable.)
*/
public PriorityQueue() {
this(DEFAULT_INITIAL_CAPACITY);
@@ -80,7 +74,7 @@ public class PriorityQueue extends Ab
/**
* Create a new priority queue with the specified initial capacity
- * that orders its elements according to their natural ordering.
+ * that orders its elements according to their natural ordering (using Comparable.)
*
* @param initialCapacity the initial capacity for this priority queue.
*/
@@ -109,8 +103,8 @@ public class PriorityQueue extends Ab
* implements the {@link Sorted} interface, 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. If the specified collection does not implement the
- * Sorted interface, the priority queue is ordered according to
+ * natural order. If the specified collection does not implement
+ * Sorted, the priority queue is ordered according to
* its elements' natural order.
*
* @param initialElements the collection whose elements are to be placed
@@ -129,11 +123,15 @@ public class PriorityQueue extends Ab
initialCapacity = 1;
queue = new E[initialCapacity + 1];
+ /* Commented out to compile with generics compiler
+
if (initialElements instanceof Sorted) {
comparator = ((Sorted)initialElements).comparator();
for (Iterator i = initialElements.iterator(); i.hasNext(); )
queue[++size] = i.next();
} else {
+ */
+ {
comparator = null;
for (Iterator i = initialElements.iterator(); i.hasNext(); )
add(i.next());
@@ -144,7 +142,7 @@ public class PriorityQueue extends Ab
/**
* Remove and return the minimal element from this priority queue if
- * it contains one or more elements, otherwise null. The term
+ * it contains one or more elements, otherwise return null. The term
* minimal is defined according to this priority queue's order.
*
* @return the minimal element from this priority queue if it contains
@@ -158,10 +156,10 @@ public class PriorityQueue extends Ab
/**
* Return, but do not remove, the minimal element from the priority queue,
- * or null if the queue is empty. The term minimal is
+ * or return null if the queue is empty. The term minimal is
* defined according to this priority queue's order. This method returns
* the same object reference that would be returned by by the
- * poll method. The two methods differ in that this method
+ * poll method. The two methods differ in that this method
* does not remove the element from the priority queue.
*
* @return the minimal element from this priority queue if it contains
@@ -179,11 +177,11 @@ public class PriorityQueue extends Ab
* specified element (or equivalently, if this collection changed as a
* result of the call).
*
- * @param o element to be removed from this collection, if present.
+ * @param element the element to be removed from this collection, if present.
* @return true if this collection changed as a result of the
* call
* @throws ClassCastException if the specified element cannot be compared
- * with elements currently in the priority queue according
+ * with elements currently in the priority queue according
* to the priority queue's ordering.
* @throws NullPointerException if the specified element is null.
*/
@@ -211,52 +209,53 @@ public class PriorityQueue extends Ab
/**
* Returns an iterator over the elements in this priority queue. The
- * first element returned by this iterator is the same element that
- * would be returned by a call to peek.
- *
+ * elements of the priority queue will be returned by this iterator in the
+ * order specified by the queue, which is to say the order they would be
+ * returned by repeated calls to poll.
+ *
* @return an Iterator over the elements in this priority queue.
*/
public Iterator iterator() {
- return new Itr();
+ return new Itr();
}
private class Itr implements Iterator {
- /**
- * Index (into queue array) of element to be returned by
+ /**
+ * Index (into queue array) of element to be returned by
* subsequent call to next.
- */
- 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.
- */
- 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.
- */
- int expectedModCount = modCount;
+ */
+ int cursor = 1;
- public boolean hasNext() {
- return cursor <= size;
- }
+ /**
+ * 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.
+ */
+ 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.
+ */
+ int expectedModCount = modCount;
+
+ public boolean hasNext() {
+ return cursor <= size;
+ }
- public E next() {
+ public E next() {
checkForComodification();
if (cursor > size)
- throw new NoSuchElementException();
+ throw new NoSuchElementException();
E result = queue[cursor];
lastRet = cursor++;
return result;
- }
+ }
- public void remove() {
- if (lastRet == 0)
- throw new IllegalStateException();
+ public void remove() {
+ if (lastRet == 0)
+ throw new IllegalStateException();
checkForComodification();
PriorityQueue.this.remove(lastRet);
@@ -264,17 +263,17 @@ public class PriorityQueue extends Ab
cursor--;
lastRet = 0;
expectedModCount = modCount;
- }
+ }
- final void checkForComodification() {
- if (modCount != expectedModCount)
- throw new ConcurrentModificationException();
- }
+ 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() {
@@ -287,7 +286,7 @@ public class PriorityQueue extends Ab
* @param element the element to add.
* @return true
* @throws ClassCastException if the specified element cannot be compared
- * with elements currently in the priority queue according
+ * with elements currently in the priority queue according
* to the priority queue's ordering.
* @throws NullPointerException if the specified element is null.
*/
@@ -406,9 +405,49 @@ public class PriorityQueue extends Ab
* null if it uses its elements' natural ordering.
*
* @return the comparator associated with this priority queue, or
- * null if it uses its elements' natural ordering.
+ * null if it uses its elements' natural ordering.
*/
- Comparator comparator() {
+ Comparator 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
+ * Object) in the proper order.
+ */
+ private synchronized 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; iArrayList instance from a stream (that is,
+ * deserialize it).
+ */
+ private synchronized 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 E[arrayLength];
+
+ // Read in all elements in the proper order.
+ for (int i=0; i