implements java.io.Serializable {

private static final long serialVersionUID = -7720805057305804111L;

private static final int DEFAULT_INITIAL_CAPACITY = 11;

/**

transient Object[] queue; // non-private to simplify nested class access

/**

private int size = 0;

/**

private final Comparator<? super E> comparator;

/**

transient int modCount = 0; // non-private to simplify nested class access

/**

public PriorityQueue() {

this(DEFAULT_INITIAL_CAPACITY, null);

}

/**

public PriorityQueue(int initialCapacity) {

this(initialCapacity, null);

}

/**

public PriorityQueue(Comparator<? super E> comparator) {

this(DEFAULT_INITIAL_CAPACITY, comparator);

}

/**

public PriorityQueue(int initialCapacity,

Comparator<? super E> comparator) {

// Note: This restriction of at least one is not actually needed,

// but continues for 1.5 compatibility

if (initialCapacity < 1)

throw new IllegalArgumentException();

this.queue = new Object[initialCapacity];

this.comparator = comparator;

}

/**

@SuppressWarnings("unchecked")

public PriorityQueue(Collection<? extends E> c) {

if (c instanceof SortedSet<?>) {

SortedSet<? extends E> ss = (SortedSet<? extends E>) c;

this.comparator = (Comparator<? super E>) ss.comparator();

initElementsFromCollection(ss);

}

else if (c instanceof PriorityQueue<?>) {

PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;

this.comparator = (Comparator<? super E>) pq.comparator();

initFromPriorityQueue(pq);

}

else {

this.comparator = null;

initFromCollection(c);

}

}

/**

@SuppressWarnings("unchecked")

public PriorityQueue(PriorityQueue<? extends E> c) {

this.comparator = (Comparator<? super E>) c.comparator();

initFromPriorityQueue(c);

}

/**

@SuppressWarnings("unchecked")

public PriorityQueue(SortedSet<? extends E> c) {

this.comparator = (Comparator<? super E>) c.comparator();

initElementsFromCollection(c);

}

private void initFromPriorityQueue(PriorityQueue<? extends E> c) {

if (c.getClass() == PriorityQueue.class) {

this.queue = c.toArray();

this.size = c.size();

} else {

initFromCollection(c);

}

}

private void initElementsFromCollection(Collection<? extends E> c) {

Object[] a = c.toArray();

// If c.toArray incorrectly doesn't return Object[], copy it.

if (a.getClass() != Object[].class)

a = Arrays.copyOf(a, a.length, Object[].class);

int len = a.length;

if (len == 1 || this.comparator != null)

for (int i = 0; i < len; i++)

if (a[i] == null)

throw new NullPointerException();

this.queue = a;

this.size = a.length;

}

/**

private void initFromCollection(Collection<? extends E> c) {

initElementsFromCollection(c);

heapify();

}

/**

private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

/**

private void grow(int minCapacity) {

int oldCapacity = queue.length;

// Double size if small; else grow by 50%

int newCapacity = oldCapacity + ((oldCapacity < 64) ?

(oldCapacity + 2) :

(oldCapacity >> 1));

// overflow-conscious code

if (newCapacity - MAX_ARRAY_SIZE > 0)

newCapacity = hugeCapacity(minCapacity);

queue = Arrays.copyOf(queue, newCapacity);

}

private static int hugeCapacity(int minCapacity) {

if (minCapacity < 0) // overflow

throw new OutOfMemoryError();

return (minCapacity > MAX_ARRAY_SIZE) ?

Integer.MAX_VALUE :

MAX_ARRAY_SIZE;

}

/**

public boolean add(E e) {

return offer(e);

}

/**

public boolean offer(E e) {

if (e == null)

throw new NullPointerException();

modCount++;

int i = size;

if (i >= queue.length)

grow(i + 1);

size = i + 1;

if (i == 0)

queue[0] = e;

else

siftUp(i, e);

return true;

}

@SuppressWarnings("unchecked")

public E peek() {

return (size == 0) ? null : (E) queue[0];

}

private int indexOf(Object o) {

if (o != null) {

for (int i = 0; i < size; i++)

if (o.equals(queue[i]))

return i;

}

return -1;

}

/**

public boolean remove(Object o) {

int i = indexOf(o);

if (i == -1)

return false;

else {

removeAt(i);

return true;

}

}

/**

boolean removeEq(Object o) {

for (int i = 0; i < size; i++) {

if (o == queue[i]) {

removeAt(i);

return true;

}

}

return false;

}

/**

public boolean contains(Object o) {

return indexOf(o) != -1;

}

/**

public Object[] toArray() {

return Arrays.copyOf(queue, size);

}

/**

@SuppressWarnings("unchecked")

public <T> T[] toArray(T[] a) {

final int size = this.size;

if (a.length < size)

// Make a new array of a's runtime type, but my contents:

return (T[]) Arrays.copyOf(queue, size, a.getClass());

System.arraycopy(queue, 0, a, 0, size);

if (a.length > size)

a[size] = null;

return a;

}

/**

public Iterator<E> iterator() {

return new Itr();

}

private final class Itr implements Iterator<E> {

/**

private int cursor = 0;

/**

private int lastRet = -1;

/**

private ArrayDeque<E> forgetMeNot = null;

/**

private E lastRetElt = null;

/**

private int expectedModCount = modCount;

public boolean hasNext() {

return cursor < size ||

(forgetMeNot != null && !forgetMeNot.isEmpty());

}

@SuppressWarnings("unchecked")

public E next() {

if (expectedModCount != modCount)

throw new ConcurrentModificationException();

if (cursor < size)

return (E) queue[lastRet = cursor++];

if (forgetMeNot != null) {

lastRet = -1;

lastRetElt = forgetMeNot.poll();

if (lastRetElt != null)

return lastRetElt;

}

throw new NoSuchElementException();

}

public void remove() {

if (expectedModCount != modCount)

throw new ConcurrentModificationException();

if (lastRet != -1) {

E moved = PriorityQueue.this.removeAt(lastRet);

lastRet = -1;

if (moved == null)

cursor--;

else {

if (forgetMeNot == null)

forgetMeNot = new ArrayDeque<>();

forgetMeNot.add(moved);

}

} else if (lastRetElt != null) {

PriorityQueue.this.removeEq(lastRetElt);

lastRetElt = null;

} else {

throw new IllegalStateException();

}

expectedModCount = modCount;

}

}

public int size() {

return size;

}

/**

public void clear() {

modCount++;

for (int i = 0; i < size; i++)

queue[i] = null;

size = 0;

}

@SuppressWarnings("unchecked")

public E poll() {

if (size == 0)

return null;

int s = --size;

modCount++;

E result = (E) queue[0];

E x = (E) queue[s];

queue[s] = null;

if (s != 0)

siftDown(0, x);

return result;

}

/**

@SuppressWarnings("unchecked")

private E removeAt(int i) {

// assert i >= 0 && i < size;

modCount++;

int s = --size;

if (s == i) // removed last element

queue[i] = null;

else {

E moved = (E) queue[s];

queue[s] = null;

siftDown(i, moved);

if (queue[i] == moved) {

siftUp(i, moved);

if (queue[i] != moved)

return moved;

}

}

return null;

}

/**

private void siftUp(int k, E x) {

if (comparator != null)

siftUpUsingComparator(k, x);

else

siftUpComparable(k, x);

}

@SuppressWarnings("unchecked")

private void siftUpComparable(int k, E x) {

Comparable<? super E> key = (Comparable<? super E>) x;

while (k > 0) {

int parent = (k - 1) >>> 1;

Object e = queue[parent];

if (key.compareTo((E) e) >= 0)

break;

queue[k] = e;

k = parent;

}

queue[k] = key;

}

@SuppressWarnings("unchecked")

private void siftUpUsingComparator(int k, E x) {

while (k > 0) {

int parent = (k - 1) >>> 1;

Object e = queue[parent];

if (comparator.compare(x, (E) e) >= 0)

break;

queue[k] = e;

k = parent;

}

queue[k] = x;

}

/**

private void siftDown(int k, E x) {

if (comparator != null)

siftDownUsingComparator(k, x);

else

siftDownComparable(k, x);

}

@SuppressWarnings("unchecked")

private void siftDownComparable(int k, E x) {

Comparable<? super E> key = (Comparable<? super E>)x;

int half = size >>> 1; // loop while a non-leaf

while (k < half) {

int child = (k << 1) + 1; // assume left child is least

Object c = queue[child];

int right = child + 1;

if (right < size &&

((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)

c = queue[child = right];

if (key.compareTo((E) c) <= 0)

break;

queue[k] = c;

k = child;

}

queue[k] = key;

}

@SuppressWarnings("unchecked")

private void siftDownUsingComparator(int k, E x) {

int half = size >>> 1;

while (k < half) {

int child = (k << 1) + 1;

Object c = queue[child];

int right = child + 1;

if (right < size &&

comparator.compare((E) c, (E) queue[right]) > 0)

c = queue[child = right];

if (comparator.compare(x, (E) c) <= 0)

break;

queue[k] = c;

k = child;

}

queue[k] = x;

}

/**

@SuppressWarnings("unchecked")

private void heapify() {

for (int i = (size >>> 1) - 1; i >= 0; i--)

siftDown(i, (E) queue[i]);

}

/**

public Comparator<? super E> comparator() {

return comparator;

}

/**

private void writeObject(java.io.ObjectOutputStream s)

throws java.io.IOException {

// Write out element count, and any hidden stuff

s.defaultWriteObject();

// Write out array length, for compatibility with 1.5 version

s.writeInt(Math.max(2, size + 1));

// Write out all elements in the "proper order".

for (int i = 0; i < size; i++)

s.writeObject(queue[i]);

}

/**

private void readObject(java.io.ObjectInputStream s)

throws java.io.IOException, ClassNotFoundException {

// Read in size, and any hidden stuff

s.defaultReadObject();

// Read in (and discard) array length

s.readInt();

queue = new Object[size];

// Read in all elements.

for (int i = 0; i < size; i++)

queue[i] = s.readObject();

// Elements are guaranteed to be in "proper order", but the

// spec has never explained what that might be.

heapify();

}

/**

public final Spliterator<E> spliterator() {

return new PriorityQueueSpliterator<E>(this, 0, -1, 0);

}

static final class PriorityQueueSpliterator<E> implements Spliterator<E> {

/*

private final PriorityQueue<E> pq;

private int index; // current index, modified on advance/split

private int fence; // -1 until first use

private int expectedModCount; // initialized when fence set

/** Creates new spliterator covering the given range */

PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,

int expectedModCount) {

this.pq = pq;

this.index = origin;

this.fence = fence;

this.expectedModCount = expectedModCount;

}

private int getFence() { // initialize fence to size on first use

int hi;

if ((hi = fence) < 0) {

expectedModCount = pq.modCount;

hi = fence = pq.size;

}

return hi;

}

public PriorityQueueSpliterator<E> trySplit() {

int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;

return (lo >= mid) ? null :

new PriorityQueueSpliterator<E>(pq, lo, index = mid,

expectedModCount);

}

@SuppressWarnings("unchecked")

public void forEachRemaining(Consumer<? super E> action) {

int i, hi, mc; // hoist accesses and checks from loop

PriorityQueue<E> q; Object[] a;

if (action == null)

throw new NullPointerException();

if ((q = pq) != null && (a = q.queue) != null) {

if ((hi = fence) < 0) {

mc = q.modCount;

hi = q.size;

}

else

mc = expectedModCount;

if ((i = index) >= 0 && (index = hi) <= a.length) {

for (E e;; ++i) {

if (i < hi) {

if ((e = (E) a[i]) == null) // must be CME

break;

action.accept(e);

}

else if (q.modCount != mc)

break;

else

return;

}

}

}

throw new ConcurrentModificationException();

}

public boolean tryAdvance(Consumer<? super E> action) {

if (action == null)

throw new NullPointerException();

int hi = getFence(), lo = index;

if (lo >= 0 && lo < hi) {

index = lo + 1;

@SuppressWarnings("unchecked") E e = (E)pq.queue[lo];

if (e == null)

throw new ConcurrentModificationException();

action.accept(e);

if (pq.modCount != expectedModCount)

throw new ConcurrentModificationException();

return true;

}

return false;

}

public long estimateSize() {

return (long) (getFence() - index);

}

public int characteristics() {

return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;

}

}