почему не проходит валидация, по всем условиям я смотрю, и все прописано правильно.
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;
}
@Override
public boolean equals(Object obj) {
if (obj == null) return false;
if (!(obj instanceof Solution)) return false;
Solution solution = (Solution) obj;
if (solution == this) return true;
if (first != null && first.equals(solution.first)) {
return last != null && last.equals(solution.last);
}
return false;
}
public int hashCode() {
int result = first != null ? first.hashCode() : -1;
result = 54 * result + (last != null ? last.hashCode() : -1);
return result;
}
public static void main(String[] args) {
Set<Solution> s = new HashSet<>();
s.add(new Solution("Donald", "Duck"));
System.out.println(s.contains(new Solution("Donald", "Duck")));
}
}