В IDEA тоже выдает на Contains False, хотя вот так вот прекрасно работает:
for (Solution m:s) System.out.println(m.equals(new Solution("Donald", "Duck")));
и выдает True.
package com.javarush.task.task21.task2104;
import java.util.HashSet;
import java.util.Set;
import java.io.*;
import java.util.*;
/*
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;
Solution o = (Solution) n;
return ((o.first != null ? o.first.equals(this.first) : false) && (o.last != null ? o.last.equals(this.last) : false));
}
@Override
public int hashCode() {
return (first==null?0:(int)(first.charAt(first.length()-1)))*31+(int)(last==null?0:(last.charAt(last.length()-1)));
}
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")));
}
}