Display Page (Pagination), Java

Display Page (Pagination)

//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

import java.util.*;
import java.lang.*;

class Rextester
{  
    public static void main(String args[])
    {
        //hostId, ListId, points, city
        List<String> input = new ArrayList<>();
        input.add("1,28,310.6,SF");
        input.add("1,5,204.1,SF");
        input.add("20,7,203.2,Oakland");
        input.add("6,8,202.2,SF");
        input.add("6,10,199.1,SF");
        input.add("1,16,190.4,SF");
        input.add("6,29,185.2,SF");
        input.add("7,20,180.1,SF");
        input.add("6,21,162.1,SF");
        input.add("2,18,161.2,SF");
        input.add("2,30,149.1,SF");
        input.add("3,76,146.2,SF");
        input.add("2,14,141.1,San Jose");
        
        List<String> result = displayPages(input, 5);
        for (int i = 0; i < result.size(); i++) {
            System.out.println(result.get(i) + "\n");
        }
        
    }
    
    static class RecordNode {
        int hostId, listId;
        double score;
        String record;
        
        public RecordNode(String record) {
            String[] tokens = record.split(",");
            hostId = Integer.valueOf(tokens[0]);
            listId = Integer.valueOf(tokens[1]);
            score = Double.valueOf(tokens[2]);
            this.record = record;
        }
    }
    
    // different hostId into different deque
    // put all deque into a priority queue sorted by the score of the head of queue
    // pop pageSize element from priority queue to form a page
    // put back the popped element back into priority queue with head element removed if not empty
    public static List<String> displayPages(List<String> records, int size) {
        Map<Integer, Deque<RecordNode>> map = new HashMap<>();
        for (String s: records) {
            RecordNode node = new RecordNode(s);
            if (!map.containsKey(node.hostId)) map.put(node.hostId, new ArrayDeque<>());
            map.get(node.hostId).offerLast(node);
        }
        PriorityQueue<Deque<RecordNode>> pq = new PriorityQueue<>((a, b) -> b.peekFirst().score > a.peekFirst().score ? 1 : -1);
        for (Deque<RecordNode> i: map.values()) pq.offer(i);
        List<String> pages = new ArrayList<>();
        List<String> lines = new ArrayList<>();
        while (!pq.isEmpty()) {
            List<Deque<RecordNode>> hold = new ArrayList<>();
            while (lines.size() < size && !pq.isEmpty()) {
                lines.add(pq.peek().peekFirst().record);
                hold.add(pq.poll());
            }
            if (lines.size() == size) {
                pages.add(String.join("\n", lines));
                lines.clear();
            }
            for (Deque<RecordNode> i: hold) {
                i.pollFirst();
                if (!i.isEmpty()) pq.offer(i);
            }
        }
        if (!lines.isEmpty()) pages.add(String.join("\n", lines));
        return pages;
    }
}


run \| edit \| history \| help	0