--- jsr166/src/main/java/util/PriorityQueue.java 2003/06/23 02:26:15 1.6
+++ jsr166/src/main/java/util/PriorityQueue.java 2003/07/28 16:00:19 1.14
@@ -3,33 +3,43 @@
/**
* 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 TreeSet} and {@link TreeMap}: elements are ordered
+ * 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
- * elements are tied for least value, no guarantees are made as to
- * which of these elements is returned.
+ * 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.
*
- * 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.
+ *
The {@link #remove()} and {@link #poll()} methods remove and
+ * return the head of the queue.
*
- *
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,
+ *
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
+ * 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).
*
*
This class is a member of the
*
* Java Collections Framework.
+ * @since 1.5
+ * @author Josh Bloch
*/
public class PriorityQueue extends AbstractQueue
- implements Queue
-{
+ implements Queue, java.io.Serializable {
+
private static final int DEFAULT_INITIAL_CAPACITY = 11;
/**
@@ -65,16 +75,18 @@ public class PriorityQueue extends Ab
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 (using Comparable.)
+ * 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
- * that orders its elements according to their natural ordering (using Comparable.)
+ * Create a PriorityQueue with the specified initial capacity
+ * that orders its elements according to their natural ordering
+ * (using Comparable.)
*
* @param initialCapacity the initial capacity for this priority queue.
*/
@@ -83,21 +95,23 @@ 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.
*/
public PriorityQueue(int initialCapacity, Comparator comparator) {
if (initialCapacity < 1)
initialCapacity = 1;
- queue = new E[initialCapacity + 1];
+ queue = (E[]) 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
* implements the {@link Sorted} interface, the priority queue will be
@@ -121,17 +135,13 @@ public class PriorityQueue extends Ab
Integer.MAX_VALUE - 1);
if (initialCapacity < 1)
initialCapacity = 1;
- queue = new E[initialCapacity + 1];
-
- /* Commented out to compile with generics compiler
+ queue = (E[]) new Object[initialCapacity + 1];
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());
@@ -141,64 +151,78 @@ public class PriorityQueue extends Ab
// 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.
+ * @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 = (E[]) new Object[2 * queue.length];
+ System.arraycopy(queue, 0, newQueue, 0, queue.length);
+ queue = newQueue;
+ }
+
+ queue[size] = element;
+ fixUp(size);
+ return true;
+ }
+
public E poll() {
if (size == 0)
return null;
return 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];
}
// 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 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 remove(Object element) {
- if (element == null)
+ public boolean add(E element) {
+ return super.add(element);
+ }
+
+ /**
+ * @throws NullPointerException if any element is null.
+ */
+ public boolean addAll(Collection c) {
+ return super.addAll(c);
+ }
+
+ /**
+ * @throws NullPointerException if the specified element is null.
+ */
+ public boolean remove(Object o) {
+ if (o == null)
throw new NullPointerException();
if (comparator == null) {
for (int i = 1; i <= size; i++) {
- if (((Comparable)queue[i]).compareTo(element) == 0) {
+ if (((Comparable)queue[i]).compareTo(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(queue[i], (E)o) == 0) {
remove(i);
return true;
}
@@ -212,50 +236,50 @@ public class PriorityQueue extends Ab
* 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;
+ */
+ 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.
- */
- 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;
- }
+ /**
+ * 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() {
+ 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);
@@ -263,17 +287,17 @@ 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() {
@@ -281,33 +305,6 @@ 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++;
-
- // Grow backing store if necessary
- if (++size == queue.length) {
- E[] newQueue = new E[2 * queue.length];
- System.arraycopy(queue, 0, newQueue, 0, size);
- queue = newQueue;
- }
-
- queue[size] = element;
- fixUp(size);
- return true;
- }
-
- /**
* Remove all elements from the priority queue.
*/
public void clear() {
@@ -400,14 +397,7 @@ public class PriorityQueue extends Ab
}
}
- /**
- * 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.
- */
- Comparator comparator() {
+ public Comparator comparator() {
return comparator;
}
@@ -418,36 +408,39 @@ public class PriorityQueue extends Ab
* @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.
+ * @param s the stream
*/
private synchronized void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException{
- // Write out element count, and any hidden stuff
- s.defaultWriteObject();
+ // 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).
+ * @param s the stream
*/
private synchronized void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
- // Read in size, and any hidden stuff
- s.defaultReadObject();
+ // Read in size, and any hidden stuff
+ s.defaultReadObject();
// Read in array length and allocate array
int arrayLength = s.readInt();
- queue = new E[arrayLength];
+ queue = (E[]) new Object[arrayLength];
- // Read in all elements in the proper order.
- for (int i=0; i