Уже по разному попробовал и не получается всё равно
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 o) {
if(this == o) return true;
if(o == null || !(o instanceof Solution)) {
return false;
}
Solution n = (Solution) o;
if(this.first == null || this.last == null) return false;
return n.first.equals(this.first) && n.last.equals(this.last);
}
public int hashCode() {
return 31 * first.hashCode() + last.hashCode();
}
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")));
}
}