java - HashSet contains() method -

i executed below code , found output false.

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")));     } } 

i want know how behaves , why output false.

you need override hashcode() method along equals(). both methods used proper functionality of hashset, must overriden in user-defined class if making class key, else hashcode() of object class getting used , no 2 different objects can considered same hashcode() different, , sure return falsealways in case of contains().