How to make an unique id for an object that is not random

Question

Problem

I need to create a unique id for each Person object.

public interface Person 
{
    String getName();
}

public class Chef implements Person
{
    String name;
    ....
    // all other instance variables are not unique to this object.
}
public class Waiter implements Person
{
    String name;
    ....
    // all other instance variables are not unique to this object.
}

---

Extra information

All other instance variables inside the Chef are not unique to a particular Chef. Nor can we add any extra variables inside the Chef class to make it unique. This is because this information is coming from a back-end server and I cannot modify the Chef class. This is a distributed system.

What I am trying to do

I want to create an integer that lets me map this Person object. I have tried to create a "unique" id.

private int makeId(Person person)
{
    int id = person.getName()
        .concat(person.getClass().getSimpleName())
        .hashCode();

    return id;
}

However, I know that this is not really unique because hashCode for a name is not guaranteeing anything uniqueness.

Without using random can I make this id unique?

I apologize for the misunderstanding, but I cannot add more fields to my Chef or Waiter object class and the application is distributed.

Answer 1

What about adding a globally unique identifier (GUID)?

A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very low probability of being duplicated.

In Java, it is called a UUID. For example:

UUID uuid = java.util.UUID.randomUUID();

System.out.println(uuid.toString());