是否有具有固定容量和自定义比较器的PriorityQueue实现？

本文介绍了是否有具有固定容量和自定义比较器的PriorityQueue实现？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 相关问题： 具有固定大小的Java PriorityQueue 如何使用PriorityQueue？ 获取数组中n个最小元素的索引 Scala：有没有办法像在Java中那样使用PriorityQueue？ / a> Java PriorityQueue with fixed sizeHow do I use a PriorityQueue?get indexes of n smallest elements in an arrayScala: Is there a way to use PriorityQueue like I would in Java?我有一个非常大的数据集（超过500万件）我需要从中获取 N个最大项目。最自然的方法是使用堆/优先级队列仅存储前N个项。 JVM（Scala / Java）的优先级队列有几个很好的实现，即：I have a very large data set (more than 5 millions items) and I need to get N largest items from it. The most natural way to do it is to use heap/priority queue storing only top N items. There are several good implementations of priority queue for JVM (Scala/Java), namely: scala.collection.mutable.PriorityQueue java.util.PriorityQueue lucene.util.PriorityQueue scala.collection.mutable.PriorityQueuejava.util.PriorityQueuelucene.util.PriorityQueue前两个很好，但它们存储了所有项目，在我的情况下会产生关键的内存开销。第三个（Lucene实现）没有这样的缺点，但正如我从文档中看到的那样，它也不支持自定义比较器，这对我来说没用。 First 2 are nice, but they store all the items, which in my case gives critical memory overhead. Third (Lucene implementation) doesn't have such a drawback, but as I can see from documentation it also doesn't support custom comparator, which makes it useless for me. 所以，我的问题是：是否 PriorityQueue 实施 固定容量和自定义比较器？So, my question is: Is there a PriorityQueue implementation with fixed capacity and custom comparator? UPD。最后我创建了自己的实现，根据Peter的回答：UPD. Finally I've created my own implementation, based on Peter's answer:public class FixedSizePriorityQueue<E> extends TreeSet<E> { private int elementsLeft; public FixedSizePriorityQueue(int maxSize) { super(new NaturalComparator()); this.elementsLeft = maxSize; } public FixedSizePriorityQueue(int maxSize, Comparator<E> comparator) { super(comparator); this.elementsLeft = maxSize; } /** * @return true if element was added, false otherwise * */ @Override public boolean add(E e) { if (elementsLeft == 0 && size() == 0) { // max size was initiated to zero => just return false return false; } else if (elementsLeft > 0) { // queue isn't full => add element and decrement elementsLeft boolean added = super.add(e); if (added) { elementsLeft--; } return added; } else { // there is already 1 or more elements => compare to the least int compared = super.comparator().compare(e, this.first()); if (compared == 1) { // new element is larger than the least in queue => pull the least and add new one to queue pollFirst(); super.add(e); return true; } else { // new element is less than the least in queue => return false return false; } } }}（其中 NaturalComparator 取自这个问题）推荐答案你可以使用SortedSet例如具有自定义比较器的TreeSet，当大小达到N时删除最小值。You could use a SortedSet e.g. TreeSet with a custom comparator and remove the smallest when the size reachs N. 这篇关于是否有具有固定容量和自定义比较器的PriorityQueue实现？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！