По какой то причине не принимает задачу по последнему пункту. Результат выдает верный.
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 (this == obj) return true;
if (!(obj instanceof Solution)) return false;
Solution sol = (Solution) obj;
return this.first == sol.first && this.last == sol.last;
}
@Override
public int hashCode() {
if (this.first == null) return 31 * (0 + this.last.length());
if (this.last == null) return 31 * (this.first.length() + 0);
if (this.first == null && this.last == null) return 0;
return 13 * (this.first.length() + this.last.length());
}
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")));
}
}