Question

I have a class (below). I have the field id for the class but I dont know how to make this create a unique id increasing sequentially.

I found that UUID.randomUUID(); would generate a unique ID but in a very unfriendly way and with no way to limit size.

How could I implement something to increase the id field as objects are created from the below class?

class Customer {

public int id;
public String name;
public String email;
public String number;
public String issue;
public String expiry;

Customer(String eName, String eEmail, String eNumber, String eIssue, String eExpiry)
{
    id = 0935091285;
    name = eName;
    email = eEmail;
    number = eNumber;
    issue = eIssue;
    expiry = eExpiry;
}
}

Answer 1

You don’t specify whether you have multiple processes simultaneously generating ids. If you don’t, the following is simple and will work well:

public class Customer {
  private static AtomicInteger nextId = new AtomicInteger(0);
  private static String getNextId() {
    return Integer.toString(nextId.incrementAndGet());
  }
  public Customer(...) {
    id = getNextId();
    ...
  }
}

Format the numeric id with leading zeroes if you’d like lexicographic ordering of ids to reflect object creation order.