Example usage for java.util PriorityQueue PriorityQueue

Introduction

In this page you can find the example usage for java.util PriorityQueue PriorityQueue.

Prototype

public PriorityQueue(int initialCapacity, Comparator<? super E> comparator)

Source Link

Document

Creates a PriorityQueue with the specified initial capacity that orders its elements according to the specified comparator.

Usage

From source file:mondrian.olap.fun.FunUtil.java

/**
 * Julian's algorithm for stable partial sort. Improves Pedro's algorithm
 * by using a heap (priority queue) for the top {@code limit} items seen.
 * The items on the priority queue have an ordinal field, so the queue
 * can be used to generate a list of stably sorted items. (Heap sort is
 * not normally stable.)/*from w  ww . ja v a2  s . co m*/
 *
 * @param list List to sort
 * @param comp Comparator
 * @param limit Maximum number of items to return
 * @param <T> Element type
 * @return Sorted list, containing at most limit items
 */
public static <T> List<T> stablePartialSortJulian(final List<T> list, final Comparator<T> comp, int limit) {
    final Comparator<ObjIntPair<T>> comp2 = new Comparator<ObjIntPair<T>>() {
        public int compare(ObjIntPair<T> o1, ObjIntPair<T> o2) {
            int c = comp.compare(o1.t, o2.t);
            if (c == 0) {
                c = Util.compare(o1.i, o2.i);
            }
            return -c;
        }
    };
    int filled = 0;
    final PriorityQueue<ObjIntPair<T>> queue = new PriorityQueue<ObjIntPair<T>>(limit, comp2);
    for (T element : list) {
        if (filled < limit) {
            queue.offer(new ObjIntPair<T>(element, filled++));
        } else {
            ObjIntPair<T> head = queue.element();
            if (comp.compare(element, head.t) <= 0) {
                ObjIntPair<T> item = new ObjIntPair<T>(element, filled++);
                if (comp2.compare(item, head) >= 0) {
                    ObjIntPair poll = queue.remove();
                    Util.discard(poll);
                    queue.offer(item);
                }
            }
        }
    }

    int n = queue.size();
    final Object[] elements = new Object[n];
    while (n > 0) {
        elements[--n] = queue.poll().t;
    }
    assert queue.isEmpty();
    //noinspection unchecked
    return Arrays.asList((T[]) elements);
}

From source file:org.apache.accumulo.tserver.tablet.Tablet.java

private Set<FileRef> removeSmallest(Map<FileRef, DataFileValue> filesToCompact, int maxFilesToCompact) {
    // ensure this method works properly when multiple files have the same size

    // short-circuit; also handles zero files case
    if (filesToCompact.size() <= maxFilesToCompact) {
        Set<FileRef> smallestFiles = new HashSet<FileRef>(filesToCompact.keySet());
        filesToCompact.clear();/*from   www.ja v a2  s  .co  m*/
        return smallestFiles;
    }

    PriorityQueue<Pair<FileRef, Long>> fileHeap = new PriorityQueue<Pair<FileRef, Long>>(filesToCompact.size(),
            new Comparator<Pair<FileRef, Long>>() {
                @Override
                public int compare(Pair<FileRef, Long> o1, Pair<FileRef, Long> o2) {
                    if (o1.getSecond() == o2.getSecond())
                        return o1.getFirst().compareTo(o2.getFirst());
                    if (o1.getSecond() < o2.getSecond())
                        return -1;
                    return 1;
                }
            });

    for (Iterator<Entry<FileRef, DataFileValue>> iterator = filesToCompact.entrySet().iterator(); iterator
            .hasNext();) {
        Entry<FileRef, DataFileValue> entry = iterator.next();
        fileHeap.add(new Pair<FileRef, Long>(entry.getKey(), entry.getValue().getSize()));
    }

    Set<FileRef> smallestFiles = new HashSet<FileRef>();
    while (smallestFiles.size() < maxFilesToCompact && fileHeap.size() > 0) {
        Pair<FileRef, Long> pair = fileHeap.remove();
        filesToCompact.remove(pair.getFirst());
        smallestFiles.add(pair.getFirst());
    }

    return smallestFiles;
}

From source file:org.apache.accumulo.server.tabletserver.Tablet.java

private Set<FileRef> removeSmallest(Map<FileRef, Long> filesToCompact, int maxFilesToCompact) {
    // ensure this method works properly when multiple files have the same size

    PriorityQueue<Pair<FileRef, Long>> fileHeap = new PriorityQueue<Pair<FileRef, Long>>(filesToCompact.size(),
            new Comparator<Pair<FileRef, Long>>() {
                @Override/*w  w w. j a  v  a  2  s .c  o  m*/
                public int compare(Pair<FileRef, Long> o1, Pair<FileRef, Long> o2) {
                    if (o1.getSecond() == o2.getSecond())
                        return o1.getFirst().compareTo(o2.getFirst());
                    if (o1.getSecond() < o2.getSecond())
                        return -1;
                    return 1;
                }
            });

    for (Iterator<Entry<FileRef, Long>> iterator = filesToCompact.entrySet().iterator(); iterator.hasNext();) {
        Entry<FileRef, Long> entry = iterator.next();
        fileHeap.add(new Pair<FileRef, Long>(entry.getKey(), entry.getValue()));
    }

    Set<FileRef> smallestFiles = new HashSet<FileRef>();
    while (smallestFiles.size() < maxFilesToCompact && fileHeap.size() > 0) {
        Pair<FileRef, Long> pair = fileHeap.remove();
        filesToCompact.remove(pair.getFirst());
        smallestFiles.add(pair.getFirst());
    }

    return smallestFiles;
}

From source file:org.apache.accumulo.tserver.Tablet.java

private Set<FileRef> removeSmallest(Map<FileRef, DataFileValue> filesToCompact, int maxFilesToCompact) {
    // ensure this method works properly when multiple files have the same size

    PriorityQueue<Pair<FileRef, Long>> fileHeap = new PriorityQueue<Pair<FileRef, Long>>(filesToCompact.size(),
            new Comparator<Pair<FileRef, Long>>() {
                @Override/*from   w w w  .  j  a v  a2s  .  co m*/
                public int compare(Pair<FileRef, Long> o1, Pair<FileRef, Long> o2) {
                    if (o1.getSecond() == o2.getSecond())
                        return o1.getFirst().compareTo(o2.getFirst());
                    if (o1.getSecond() < o2.getSecond())
                        return -1;
                    return 1;
                }
            });

    for (Iterator<Entry<FileRef, DataFileValue>> iterator = filesToCompact.entrySet().iterator(); iterator
            .hasNext();) {
        Entry<FileRef, DataFileValue> entry = iterator.next();
        fileHeap.add(new Pair<FileRef, Long>(entry.getKey(), entry.getValue().getSize()));
    }

    Set<FileRef> smallestFiles = new HashSet<FileRef>();
    while (smallestFiles.size() < maxFilesToCompact && fileHeap.size() > 0) {
        Pair<FileRef, Long> pair = fileHeap.remove();
        filesToCompact.remove(pair.getFirst());
        smallestFiles.add(pair.getFirst());
    }

    return smallestFiles;
}