hashCode equals hashSet

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

public class Sets {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Person p1 = new Person("320321");
        p1.setAge(22);
        p1.setName("p1");
        Person p2 = new Person("320321");
        p2.setAge(23);
        p2.setName("p2");
        Person p3 = new Person("320322");
        p3.setAge(22);
        p3.setName("p3");
        Person p4=new Person("320321");
        p4.setAge(22);
        p4.setName("p4");
        Set<Person> hashSet = new HashSet();
        hashSet.add(p1);
        hashSet.add(p2);
        // 
        System.out.println(hashSet);
        hashSet.add(p3);
        //
        System.out.println(hashSet);
        hashSet.add(p4);
        //
        System.out.println(hashSet);
    }
}