--- jsr166/src/main/java/util/PriorityQueue.java 2003/06/24 14:34:30 1.7
+++ jsr166/src/main/java/util/PriorityQueue.java 2003/07/31 07:18:02 1.15
@@ -3,13 +3,20 @@
/**
* 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.
+ *
+ * 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
@@ -17,12 +24,12 @@
* 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
*
@@ -31,7 +38,8 @@
* @author Josh Bloch
*/
public class PriorityQueue extends AbstractQueue
- implements Queue {
+ implements Queue, java.io.Serializable {
+
private static final int DEFAULT_INITIAL_CAPACITY = 11;
/**
@@ -67,16 +75,16 @@ 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.)
*
@@ -87,23 +95,28 @@ 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) {
if (initialCapacity < 1)
- initialCapacity = 1;
- queue = new E[initialCapacity + 1];
+ throw new IllegalArgumentException();
+ 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
+ * 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'
@@ -111,33 +124,31 @@ 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];
- /* 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(); )
+ if (c instanceof Sorted) {
+ // FIXME: this code assumes too much
+ comparator = ((Sorted)c).comparator();
+ for (Iterator i = c.iterator(); i.hasNext(); )
queue[++size] = i.next();
} else {
- */
- {
comparator = null;
- for (Iterator i = initialElements.iterator(); i.hasNext(); )
+ for (Iterator i = c.iterator(); i.hasNext(); )
add(i.next());
}
}
@@ -145,67 +156,81 @@ 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 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 element) {
+ return super.add(element);
+ }
+
+ /**
+ * @throws NullPointerException if any element is null.
+ * @throws ClassCastException if any element cannot be compared
+ * with elements currently in the priority queue according
+ * to the priority queue's ordering.
+ */
+ 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(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;
}
@@ -214,14 +239,6 @@ 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();
}
@@ -280,7 +297,7 @@ 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() {
@@ -288,33 +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() {
@@ -407,14 +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;
}
@@ -452,7 +435,7 @@ public class PriorityQueue extends Ab
// 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 extends Ab
}
}
+