java – HashSet contains()方法

import java.util.Set;
import java.util.HashSet;

public class Name {
    private String first,last;

    public Name(String first,String last) {
        this.first = first;
        this.last = last;
    }

    public boolean equals(Object o) {
        if (!(o instanceof Name))
            return false;
        Name n = (Name) o;
        return n.first.equals(first) && n.last.equals(last);
    }

    public static void main(String[] args) {
        Set<Name> s = new HashSet<Name>();
        s.add(new Name("Donald","Duck"));
        System.out.println(s.contains(new Name("Donald","Duck")));
    }
}

我想知道它的行为以及为什么输出是错误的.