Сдаюсь, что я упускаю?

package com.javarush.task.task21.task2106; import java.util.Date; /* Ошибка в equals/hashCode */ public class Solution { private int anInt; private String string; private double aDouble; private Date date; private Solution solution; public Solution(int anInt, String string, double aDouble, Date date, Solution solution) { this.anInt = anInt; this.string = string; this.aDouble = aDouble; this.date = date; this.solution = solution; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || o.getClass() != this.getClass()) return false; if (o instanceof Solution) return false; Solution solution1 = (Solution) o; if (Double.compare(solution1.aDouble, aDouble) != 0) return false; if (anInt != solution1.anInt) return false; if (date != solution1.date && (date != null && !date.equals(solution1.date))) return false; if (solution != solution1.solution && (solution != null && !solution.equals(solution1.solution))) return false; if (string != solution1.string && (string != null && !string.equals(solution1.string))) return false; return true; } @Override public int hashCode() { int result; long temp; result = anInt; temp = aDouble != +0.0d ? Double.doubleToLongBits(aDouble) : 0L; result = 31 * result + (int) (temp ^ (temp >>> 32)); result = 31 * result + (date != null ? date.hashCode() : 0); result = 31 * result + (solution != null ? solution.hashCode() : 0); result = 31 * result + (string != null ? string.hashCode() : 0); return result; } public static void main(String[] args) { } }