--- jsr166/src/main/java/util/PriorityQueue.java 2003/07/13 22:51:22 1.9
+++ jsr166/src/main/java/util/PriorityQueue.java 2003/08/04 16:14:48 1.19
@@ -1,28 +1,38 @@
package java.util;
/**
- * An unbounded priority queue based on a priority heap. This queue orders
+ * A 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 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 {@link #peek}, {@link #poll}, and {@link #remove} methods return the
- * minimal element with respect to the specified ordering. If multiple
- * elements are tied for least value, no guarantees are made as to
- * which of these elements is returned.
+ * 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.
+ *
+ *
The {@link #remove()} and {@link #poll()} methods remove and
+ * return the head of the queue.
+ *
+ *
The {@link #element()} and {@link #peek()} methods return, but do
+ * not delete, the head of the queue.
*
*
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, and is limited to Integer.MAX_VALUE-1.
+ * 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 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 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).
*
*
This class is a member of the
*
@@ -31,8 +41,8 @@
* @author Josh Bloch
*/
public class PriorityQueue extends AbstractQueue
- implements Queue,
- java.io.Serializable {
+ implements Sorted, Queue, java.io.Serializable {
+
private static final int DEFAULT_INITIAL_CAPACITY = 11;
/**
@@ -48,7 +58,7 @@ public class PriorityQueue extends Ab
*
* queue.length must be >= 2, even if size == 0.
*/
- private transient E[] queue;
+ private transient Object[] queue;
/**
* The number of elements in the priority queue.
@@ -59,7 +69,7 @@ public class PriorityQueue extends Ab
* The comparator, or null if priority queue uses elements'
* natural ordering.
*/
- private final Comparator comparator;
+ private final Comparator comparator;
/**
* The number of times this priority queue has been
@@ -68,16 +78,16 @@ public class PriorityQueue extends Ab
private transient int modCount = 0;
/**
- * Create a new priority queue with the default initial capacity
+ * Create a PriorityQueue with the default initial capacity
* (11) that orders its elements according to their natural
* ordering (using Comparable.)
*/
public PriorityQueue() {
- this(DEFAULT_INITIAL_CAPACITY);
+ this(DEFAULT_INITIAL_CAPACITY, null);
}
/**
- * Create a new priority queue with the specified initial capacity
+ * Create a PriorityQueue with the specified initial capacity
* that orders its elements according to their natural ordering
* (using Comparable.)
*
@@ -88,23 +98,29 @@ public class PriorityQueue extends Ab
}
/**
- * Create a new priority queue with the specified initial capacity (11)
+ * Create 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.
* @param comparator the comparator used to order this priority queue.
+ * If null then the order depends on the elements' natural
+ * ordering.
+ * @throws IllegalArgumentException if initialCapacity is less
+ * than 1
*/
- public PriorityQueue(int initialCapacity, Comparator comparator) {
+ public PriorityQueue(int initialCapacity, Comparator comparator) {
if (initialCapacity < 1)
- initialCapacity = 1;
- queue = new E[initialCapacity + 1];
+ throw new IllegalArgumentException();
+ this.queue = new Object[initialCapacity + 1];
this.comparator = comparator;
}
/**
- * Create a new priority queue containing the elements in the specified
+ * 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. If the specified collection
+ * size of the specified collection (bounded by
+ * Integer.MAX_VALUE-1); 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'
@@ -112,98 +128,116 @@ public class PriorityQueue extends Ab
* Sorted, the priority queue is ordered according to
* its elements' natural order.
*
- * @param initialElements the collection whose elements are to be placed
+ * @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 the specified collection or an
- * element of the specified collection is null.
+ * @throws NullPointerException if c or any element within it
+ * is null
*/
- public PriorityQueue(Collection initialElements) {
- int sz = initialElements.size();
+ 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;
- queue = new E[initialCapacity + 1];
+ this.queue = new Object[initialCapacity + 1];
- if (initialElements instanceof Sorted) {
- comparator = ((Sorted)initialElements).comparator();
- for (Iterator i = initialElements.iterator(); i.hasNext(); )
- queue[++size] = i.next();
+ // FIXME: if c is larger than Integer.MAX_VALUE we'll
+ // overflow the array
+
+ if (c instanceof Sorted) {
+ comparator = (Comparator)((Sorted)c).comparator();
} else {
comparator = null;
- for (Iterator i = initialElements.iterator(); i.hasNext(); )
- add(i.next());
}
+
+ for (Iterator i = c.iterator(); i.hasNext(); )
+ add(i.next());
}
// Queue Methods
/**
- * Remove and return the minimal element from this priority queue
- * if it contains one or more elements, otherwise return
- * null. The term minimal is defined according to
- * this priority queue's order.
+ * Add the specified element to this priority queue.
*
- * @return the minimal element from this priority queue if it contains
- * one or more elements, otherwise null.
+ * @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.
*/
+ public boolean offer(E o) {
+ if (o == null)
+ throw new NullPointerException();
+ modCount++;
+ ++size;
+
+ // Grow backing store if necessary
+ // FIXME: watch for overflow
+ // FIXME: what if we're full?
+ while (size >= queue.length) {
+ Object[] newQueue = new Object[2 * queue.length];
+ System.arraycopy(queue, 0, newQueue, 0, queue.length);
+ queue = newQueue;
+ }
+
+ queue[size] = o;
+ fixUp(size);
+ return true;
+ }
+
public E poll() {
if (size == 0)
return null;
- return remove(1);
+ return (E) remove(1);
}
- /**
- * Return, but do not remove, the minimal element from the
- * priority queue, 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 does not remove the element
- * from the priority queue.
- *
- * @return the minimal element from this priority queue if it contains
- * one or more elements, otherwise null.
- */
public E peek() {
- return queue[1];
+ return (E) queue[1];
}
// Collection Methods
+ // these first two override just to get the throws docs
+
/**
- * Removes a single instance of the specified element from this priority
- * queue, if it is present. Returns true if this collection contained the
- * specified element (or equivalently, if this collection changed as a
- * result of the call).
- *
- * @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 NullPointerException if the specified element is null.
* @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.
+ * with elements currently in the priority queue according
+ * to the priority queue's ordering.
*/
- public boolean remove(Object element) {
- if (element == null)
- throw new NullPointerException();
+ 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 c or any element in c
+ * is null
+ */
+ public boolean addAll(Collection 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)queue[i]).compareTo(element) == 0) {
+ if (((Comparable)queue[i]).compareTo((E)o) == 0) {
remove(i);
return true;
}
}
} else {
for (int i = 1; i <= size; i++) {
- if (comparator.compare(queue[i], (E) element) == 0) {
+ if (comparator.compare((E)queue[i], (E)o) == 0) {
remove(i);
return true;
}
@@ -212,14 +246,6 @@ public class PriorityQueue extends Ab
return false;
}
- /**
- * Returns an iterator over the elements in this priority queue. The
- * 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();
}
@@ -253,7 +279,7 @@ public class PriorityQueue extends Ab
checkForComodification();
if (cursor > size)
throw new NoSuchElementException();
- E result = queue[cursor];
+ E result = (E) queue[cursor];
lastRet = cursor++;
return result;
}
@@ -278,7 +304,7 @@ 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() {
@@ -286,34 +312,6 @@ public class PriorityQueue extends Ab
}
/**
- * 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.
- */
- public boolean offer(E element) {
- if (element == null)
- throw new NullPointerException();
- modCount++;
- ++size;
-
- // Grow backing store if necessary
- while (size >= queue.length) {
- E[] newQueue = new E[2 * queue.length];
- System.arraycopy(queue, 0, newQueue, 0, queue.length);
- queue = newQueue;
- }
-
- queue[size] = element;
- fixUp(size);
- return true;
- }
-
- /**
* Remove all elements from the priority queue.
*/
public void clear() {
@@ -337,7 +335,7 @@ public class PriorityQueue extends Ab
assert i <= size;
modCount++;
- E result = queue[i];
+ E result = (E) queue[i];
queue[i] = queue[size];
queue[size--] = null; // Drop extra ref to prevent memory leak
if (i <= size)
@@ -358,17 +356,17 @@ public class PriorityQueue extends Ab
if (comparator == null) {
while (k > 1) {
int j = k >> 1;
- if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
+ if (((Comparable)queue[j]).compareTo((E)queue[k]) <= 0)
break;
- E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
+ Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
k = j;
}
} else {
while (k > 1) {
int j = k >> 1;
- if (comparator.compare(queue[j], queue[k]) <= 0)
+ if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
break;
- E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
+ Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
k = j;
}
}
@@ -387,33 +385,26 @@ public class PriorityQueue extends Ab
int j;
if (comparator == null) {
while ((j = k << 1) <= size) {
- if (j 0)
+ if (j)queue[j]).compareTo((E)queue[j+1]) > 0)
j++; // j indexes smallest kid
- if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
+ if (((Comparable)queue[k]).compareTo((E)queue[j]) <= 0)
break;
- E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
+ Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
k = j;
}
} else {
while ((j = k << 1) <= size) {
- if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
+ if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
j++; // j indexes smallest kid
- if (comparator.compare(queue[k], queue[j]) <= 0)
+ if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
break;
- E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
+ Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
k = j;
}
}
}
- /**
- * Returns the comparator associated with this priority queue, or
- * 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.
- */
- public Comparator comparator() {
+ public Comparator comparator() {
return comparator;
}
@@ -451,11 +442,12 @@ public class PriorityQueue extends Ab
// Read in array length and allocate array
int arrayLength = s.readInt();
- queue = new E[arrayLength];
+ queue = new Object[arrayLength];
// Read in all elements in the proper order.
for (int i=0; i