--- jsr166/src/main/java/util/PriorityQueue.java 2003/07/31 15:44:41 1.16
+++ jsr166/src/main/java/util/PriorityQueue.java 2003/08/06 18:22:09 1.24
@@ -1,14 +1,17 @@
package java.util;
/**
- * An unbounded priority queue based on a priority heap. This queue orders
+ * An unbounded priority {@linkplain Queue 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 TreeSet} and {@link TreeMap}:
- * elements are ordered
+ * specified in the same manner as {@link java.util.TreeSet} and
+ * {@link java.util.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 head of this queue is the least element with respect to the
- * specified ordering. If multiple elements are tied for least value, the
+ * according to a {@link java.util.Comparator}, depending on which
+ * constructor is used.
+ * 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. A priority queue does not permit
* null elements.
*
@@ -20,7 +23,8 @@
*
*
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
+ * 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.
*
@@ -75,27 +79,29 @@ public class PriorityQueue extends Ab
private transient int modCount = 0;
/**
- * Create a PriorityQueue with the default initial capacity
+ * Creates a PriorityQueue with the default initial capacity
* (11) that orders its elements according to their natural
- * ordering (using Comparable.)
+ * ordering (using Comparable).
*/
public PriorityQueue() {
this(DEFAULT_INITIAL_CAPACITY, null);
}
/**
- * Create a PriorityQueue with the specified initial capacity
+ * Creates a PriorityQueue with the specified initial capacity
* that orders its elements according to their natural ordering
- * (using Comparable.)
+ * (using Comparable).
*
* @param initialCapacity the initial capacity for this priority queue.
+ * @throws IllegalArgumentException if initialCapacity is less
+ * than 1
*/
public PriorityQueue(int initialCapacity) {
this(initialCapacity, null);
}
/**
- * Create a PriorityQueue with the specified initial capacity
+ * Creates a PriorityQueue with the specified initial capacity
* that orders its elements according to the specified comparator.
*
* @param initialCapacity the initial capacity for this priority queue.
@@ -105,7 +111,8 @@ public class PriorityQueue extends Ab
* @throws IllegalArgumentException if initialCapacity is less
* than 1
*/
- public PriorityQueue(int initialCapacity, Comparator comparator) {
+ public PriorityQueue(int initialCapacity,
+ Comparator comparator) {
if (initialCapacity < 1)
throw new IllegalArgumentException();
this.queue = new Object[initialCapacity + 1];
@@ -113,16 +120,51 @@ public class PriorityQueue extends Ab
}
/**
- * Create a PriorityQueue 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
- * 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
- * Sorted, the priority queue is ordered according to
- * its elements' natural order.
+ * Common code to initialize underlying queue array across
+ * constructors below.
+ */
+ private void initializeArray(Collection 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 c) {
+ for (Iterator 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 c) {
+ for (Iterator i = c.iterator(); i.hasNext(); )
+ add(i.next());
+ }
+
+ /**
+ * Creates a PriorityQueue 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
+ * PriorityQueue, 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.
@@ -133,52 +175,113 @@ public class PriorityQueue extends Ab
* is null
*/
public PriorityQueue(Collection 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];
-
- if (c instanceof Sorted) {
- // FIXME: this code assumes too much
- this.comparator = (Comparator) ((Sorted)c).comparator();
- for (Iterator i = c.iterator(); i.hasNext(); )
- queue[++size] = i.next();
- } else {
+ initializeArray(c);
+ if (c instanceof SortedSet) {
+ SortedSet s = (SortedSet) c;
+ comparator = (Comparator)s.comparator();
+ fillFromSorted(s);
+ }
+ else if (c instanceof PriorityQueue) {
+ PriorityQueue s = (PriorityQueue) c;
+ comparator = (Comparator)s.comparator();
+ fillFromSorted(s);
+ }
+ else {
comparator = null;
- for (Iterator i = c.iterator(); i.hasNext(); )
- add(i.next());
+ fillFromUnsorted(c);
}
}
+ /**
+ * Creates a PriorityQueue 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 c or any element within it
+ * is null
+ */
+ public PriorityQueue(PriorityQueue c) {
+ initializeArray(c);
+ comparator = (Comparator)c.comparator();
+ fillFromSorted(c);
+ }
+
+ /**
+ * Creates a PriorityQueue 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 c or any element within it
+ * is null
+ */
+ public PriorityQueue(SortedSet c) {
+ initializeArray(c);
+ comparator = (Comparator)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.
*
- * @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
* to the priority queue's ordering.
- * @throws NullPointerException if the specified element is null.
+ * @throws NullPointerException if the specified element is null.
*/
- public boolean offer(E element) {
- if (element == null)
+ public boolean offer(E o) {
+ if (o == null)
throw new NullPointerException();
modCount++;
++size;
// Grow backing store if necessary
- while (size >= queue.length) {
- Object[] newQueue = new Object[2 * queue.length];
- System.arraycopy(queue, 0, newQueue, 0, queue.length);
- queue = newQueue;
- }
+ if (size >= queue.length)
+ grow(size);
- queue[size] = element;
+ queue[size] = o;
fixUp(size);
return true;
}
@@ -193,22 +296,33 @@ public class PriorityQueue extends Ab
return (E) queue[1];
}
- // Collection Methods
-
- // these first two override just to get the throws docs
+ // Collection Methods - the first two override to update docs
/**
- * @throws NullPointerException if the specified element is null.
+ * Adds the specified element to this queue.
+ * @return true (as per the general contract of
+ * Collection.add).
+ *
+ * @throws NullPointerException {@inheritDoc}
* @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 element) {
- return super.add(element);
+ public boolean add(E o) {
+ return super.add(o);
}
+
/**
- * @throws NullPointerException if any element is null.
+ * Adds all of the elements in the specified collection to this queue.
+ * The behavior of this operation is undefined if
+ * the specified collection is modified while the operation is in
+ * progress. (This implies that the behavior of this call is undefined if
+ * the specified collection is this queue, and this queue is nonempty.)
+ *
+ * This implementation iterates over the specified collection, and adds
+ * each object returned by the iterator to this collection, in turn.
+ * @throws NullPointerException {@inheritDoc}
* @throws ClassCastException if any element cannot be compared
* with elements currently in the priority queue according
* to the priority queue's ordering.
@@ -217,6 +331,21 @@ public class PriorityQueue extends Ab
return super.addAll(c);
}
+
+ /**
+ * Removes a single instance of the specified element from this
+ * queue, if it is present. More formally,
+ * removes an element e such that (o==null ? e==null :
+ * o.equals(e)), if the queue contains one or more such
+ * elements. Returns true if the queue contained the
+ * specified element (or equivalently, if the queue changed as a
+ * result of the call).
+ *
+ * This implementation iterates over the queue looking for the
+ * specified element. If it finds the element, it removes the element
+ * from the queue using the iterator's remove method.
+ *
+ */
public boolean remove(Object o) {
if (o == null)
return false;
@@ -239,6 +368,12 @@ public class PriorityQueue extends Ab
return false;
}
+ /**
+ * Returns an iterator over the elements in this queue. The iterator
+ * does not return the elements in any particular order.
+ *
+ * @return an iterator over the elements in this queue.
+ */
public Iterator iterator() {
return new Itr();
}
@@ -295,11 +430,6 @@ public class PriorityQueue extends Ab
}
}
- /**
- * Returns the number of elements in this priority queue.
- *
- * @return the number of elements in this priority queue.
- */
public int size() {
return size;
}
@@ -397,6 +527,15 @@ public class PriorityQueue extends Ab
}
}
+
+ /**
+ * Returns the comparator used to order this collection, or null
+ * if this collection is sorted according to its elements natural ordering
+ * (using Comparable).
+ *
+ * @return the comparator used to order this collection, or null
+ * if this collection is sorted according to its elements natural ordering.
+ */
public Comparator comparator() {
return comparator;
}
@@ -410,7 +549,7 @@ public class PriorityQueue extends Ab
* Object) in the proper order.
* @param s the stream
*/
- private synchronized void writeObject(java.io.ObjectOutputStream s)
+ private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException{
// Write out element count, and any hidden stuff
s.defaultWriteObject();
@@ -428,7 +567,7 @@ public class PriorityQueue extends Ab
* deserialize it).
* @param s the stream
*/
- private synchronized void readObject(java.io.ObjectInputStream s)
+ private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in size, and any hidden stuff
s.defaultReadObject();