New to Java

Hi Friends,
I have a custom class Person and I would like to store only unique Person objects into a hashmap. But I am confused on how to compare objects using the hashmap's containKey method.

So,I am trying something like this:

HashMap<Person,Integer> persons = new HashMap<Person,Integer>();
Person p = new Person("tester"); //person constructor with name

//add person object only if it does not exists
if(persons.containsKey(p)){ // this is what i am confused with
 //do something
}
else{
persons.add(p,1);
}

But I am connfused how to compare objects of a particular class??? Do I need to add "equals" or some other method to the Person class or is there any other way???

Any help would be appreciated
Thanks