Добрый вечер.
Объясните, почему не проходит по последнему пункту, пожалуйста.
package com.javarush.task.task21.task2104;
import java.util.HashSet;
import java.util.Set;
/*
Equals and HashCode
*/
public class Solution {
private final String first, last;
public Solution(String first, String last) {
this.first = first;
this.last = last;
}
public boolean equals(Object n) {
if (n == this) return false;
if (!(n instanceof Solution)) return false;
Solution s = (Solution) n;
boolean b1 = s.first != null && first != null;
boolean b2 = s.last != null && last != null;
boolean b3 = b1 && s.first.equals(first);
boolean b4 = b2 && s.last.equals(last);
if (s.first == null && first == null && b4 || s.last == null && last == null && b3) return true;
return b3 && b4;
}
public int hashCode() {
int f = first != null ? first.hashCode() : 0;
int l = last != null ? last.hashCode() : 0;
return 31 * f + l;
}
public static void main(String[] args) {
Set<Solution> s = new HashSet<>();
s.add(new Solution("Donald", null));
System.out.println(s.contains(new Solution("Donald", null)));
}
}