Quest Sorting

SortQuests.java

import lombok.extern.slf4j.Slf4j;

import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

public class Test {
    public static void main(String[] args) {
        Set<Quest> quests = new HashSet<>();
        // Quest A has no dependencies
        quests.add(new Quest("quest_a", ""));
        quests.add(new Quest("quest_a1", "quest_a"));
        quests.add(new Quest("quest_a11", "quest_a1"));
        quests.add(new Quest("quest_a111", "quest_a11"));
        
        quests.add(new Quest("quest_a2", "quest_a"));
        quests.add(new Quest("quest_a22", "quest_a2"));

        quests.add(new Quest("quest_b", ""));
        quests.add(new Quest("quest_b1", "quest_b"));

        Set<String> existingQuests = new java.util.HashSet<>();
        Set<Quest> questsToSort = new java.util.HashSet<>(quests);
        // Sort the quests based on insert order
        int lastInsertedCount = 1;
        List<Set<Quest>> sortedQuests = new java.util.ArrayList<>();
        // no pre requisites
        // First line prerequisites
        // SEcond line prerequisites
        
        
        while (!questsToSort.isEmpty()) {
            if (lastInsertedCount <= 0) {
                System.out.println("Infinite recrsion, last inserted quests were: ");
                for (Quest q : sortedQuests.get(sortedQuests.size() - 1)) {
                    System.out.println(q.id);
                }
                throw new RuntimeException("Infinite recursion on quest dependencies");
            }
            lastInsertedCount = 0;
            
            Set<Quest> questsToInsert = new java.util.HashSet<>();
            for (Quest quest : questsToSort) {
                if (quest.prerequisites == null || quest.prerequisites.isEmpty() || existingQuests.containsAll(quest.prerequisites)) {
                    questsToInsert.add(quest);
                    lastInsertedCount++;
                }
            }
            // Insert quests to rocket
            existingQuests.addAll(questsToInsert.stream().map(quest -> quest.id).collect(Collectors.toSet()));
            // Remove quests from todo list
            questsToSort.removeAll(questsToInsert);
            // Add them to the sorted list
            sortedQuests.add(questsToInsert);
        }

        int round = 1;
        for (Set<Quest> questsToInsert : sortedQuests) {
            System.out.println("======= Round " + round++ + " =======");
            for (Quest quest : questsToInsert) {
                System.out.println(quest.id);
            }
        }

    }

    static class Quest {
        String id;
        Set<String> prerequisites;

        public Quest(String id, String... prerequisites) {
            this.id = id;
            this.prerequisites = new HashSet<>();
            if (prerequisites != null) {
                Arrays.stream(prerequisites).filter(p -> p != null && !p.isEmpty()).forEach(this.prerequisites::add);
            }
        }
    }

}