Почему не работает?

package com.javarush.task.task08.task0824; import java.io.IOException; import java.util.ArrayList; import java.util.Iterator; /* Собираем семейство */ public class Solution { public static void main(String[] args) throws IOException { //напишите тут ваш код ArrayList<Human> listforpareants = new ArrayList<Human>(); ArrayList<Human> listForGrandParents = new ArrayList<Human>(); ArrayList<Human> listForGrandParents2 = new ArrayList<Human>(); ArrayList<Human> all = new ArrayList<Human>(); Human son = new Human("Борис", true, 12); Human douther = new Human("Инна", false, 10); Human son2 = new Human("Глеб", true, 14); listforpareants.add(son); listforpareants.add(douther); listforpareants.add(son2); Human father = new Human ("Василий", true, 38, listforpareants); Human mother = new Human ("Анастасия", false, 36, listforpareants); listForGrandParents.add(father); listForGrandParents2.add(mother); Human grandfather = new Human("Алеша", true, 63, listForGrandParents); Human grandmother = new Human("Валентина", false, 62, listForGrandParents); Human grandfather2 = new Human("Иван", true, 61, listForGrandParents2); Human grandmother2 = new Human("Дарья", false, 60, listForGrandParents2); all.addAll(listforpareants); all.addAll(listForGrandParents); all.addAll(listForGrandParents2); all.add(grandmother); all.add(grandfather); all.add(grandmother2); all.add(grandfather2); Iterator <Human> iterator = all.iterator(); while(iterator.hasNext()) System.out.println(iterator.next()); } public static class Human { //напишите тут ваш код public String name; public boolean sex; public int age; ArrayList<Human> children; public Human (String name, boolean sex, int age){ this.name = name; this.age = age; this.sex = sex; } public Human (String name, boolean sex, int age, ArrayList<Human> children){ this.name = name; this.age = age; this.sex = sex; this.children = children; } public String toString() { String text = ""; text += "Имя: " + this.name; text += ", пол: " + (this.sex ? "мужской" : "женский"); text += ", возраст: " + this.age; int childCount = this.children.size(); if (childCount > 0) { text += ", дети: " + this.children.get(0).name; for (int i = 1; i < childCount; i++) { Human child = this.children.get(i); text += ", " + child.name; } } return text; } } }