What it will return ..... ? Just try it.

import java.util.*;
public class Name {
private final 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("Mickey", "Mouse"));
System.out.println(s.contains(new Name("Mickey", "Mouse")));
}
}