一、代码实现

public class TopNUtil<E extends Comparable<E>> {private final PriorityQueue<E> priorityQueue;private final int n;/*** 构造 Top-N*/public TopNUtil(int size) {if (size <= 0) {throw new IllegalArgumentException("Top-N size must be a positive number");}this.priorityQueue = new PriorityQueue<>(size);this.n = size;}/*** 向 Top-N 中插入元素*/public void add(E e) {if (priorityQueue.size() < n) {priorityQueue.add(e);return;}E head = priorityQueue.peek();if (head != null && e.compareTo(head) <= 0) {return;}priorityQueue.poll();priorityQueue.add(e);}/*** 将 Top-N 转为从大到小排序的 List*/public List<E> toSortedArrayList() {List<E> tempList = new ArrayList<>(priorityQueue);tempList.sort(Collections.reverseOrder());return tempList;}
}

二、使用示例

class TopNUtilTest {@Testvoid test() {List<HerbOrderPriceCountDTO> list = new ArrayList<>();TopNUtil<HerbOrderPriceCountDTO> top = new TopNUtil<>(3);// 生成 10 个随机的 DoctorFlowDTOfor (int i = 0; i < 10; i++) {HerbOrderPriceCountDTO dto = new HerbOrderPriceCountDTO();dto.setOrderPriceSum(BigDecimal.valueOf(Math.random() * 100));list.add(dto);}System.out.println("所有的 orderFlow 值:");for (HerbOrderPriceCountDTO dto : list) {System.out.print(dto.getOrderPriceSum());System.out.print(" ");}System.out.println();// 将列表中的元素添加到 TopNUtilfor (HerbOrderPriceCountDTO dto : list) {top.add(dto);}// 获取 TopNUtil 中的元素列表List<HerbOrderPriceCountDTO> topList = top.toSortedArrayList();// 确保列表的大小不超过 3assertEquals(3, topList.size());// 打印 Top 3 元素的 orderFlow 值System.out.println("Top 3 orderFlow 值:");for (HerbOrderPriceCountDTO dto : topList) {System.out.println(dto.getOrderPriceSum());}}
}