Почему то не принимает последний и предпоследний пункт.
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(Solution n) {
if (this == n) return true;
//if (!(n instanceof Solution)) return false;
if (first!=null ? !first.equals(n.first): n.first != null) return false;
return last!=null ? last.equals(n.last): n.last==null;
}
public int hashCode() {
int result=0;
result += first!=null? 31 * first.hashCode():0;
result += last!=null? 31 * last.hashCode():0;
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")));
}
}