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I am building a small project for my self and every time a Employee is created they are given an ID.

This Id is generated by finding the .size() of a ArrayList.

//Creating the Employee Id
int employeeID = listEmployee.size() +1;

I know this is a bad idea because when removing an employee the Id's will star to duplicate.

This is the function I am using when creating a Employee

 public void addHiredEmployee() {
    Scanner kb = new Scanner(System.in);


    System.out.println("Enter Name: ");
    String nameEmployee = kb.nextLine();

    //Creating Id for the employee by getting the last employee in the list 
    //getting their Id and adding 1 to it 
    Employee lastEmployee = listEmployee.get(listEmployee.size() -1);

    int idCreation = lastEmployee.getEmployeeId();
    int employeeID = idCreation + 1;

    System.out.println("Enter password");
    String employeePassword = kb.nextLine();

    System.out.println("Your log-in Id is: " + employeeID);

    Employee employeeHired = new Employee(nameEmployee, employeeID, 
    employeePassword);

    listEmployee.add(employeeHired);

    kb.close();

    listEmployee.toString();
}

I know about using UUID but as the Employee Id will be used to login I cant really expect that some one enters a full UUID.

Is there a simple way of creating a random Id or even can I use the last 4 characters of a UUID just for the login and how could I implement selecting the last 4 characters?

Liam
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  • Why not to declare a counter and increment it each time you need a new ID? – Pavel Smirnov Jan 29 '20 at 15:02
  • Does this help : https://stackoverflow.com/questions/2982748/create-a-guid-in-java – Shubham Jan 29 '20 at 15:02
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    An ID should just be a technical identifier and should not be exposed to users. Therefore it is not a good idea to use it for login purposes. Instead, add something like a nickname and use that for logging in – QBrute Jan 29 '20 at 15:04
  • Why a down vote it was a a valid question?? Explain why – Liam Jan 29 '20 at 15:05
  • @Liam I'm not downvoting, though I think this question is better suited to https://codereview.stackexchange.com/ – charlie_pl Jan 29 '20 at 15:06

3 Answers3

5

It depends on what you need the ID for. Technical IDs should in general be unique throughout the lifetime of your system. For databases, these are usually auto-increment numeric values. Rather than taking the count they store the last used id and increment it.

For login etc. you would want to use something else, such as a username. This is usually called a functional id or business id. It's still unique, but requirements are less strict. It can be reused, for example.

UUIDs are a good idea if you need to create your IDs in a highly parallel environment. While they can be generated in parallel without synchronisation, they have other drawbacks, like difficult to index, length and thus storage requirements etc.

phisch
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0

The best way to create a random Id for each Employee is to use UUID.

class that represents an immutable universally unique identifier (UUID). A UUID represents a 128-bit value. There exist different variants of these global identifiers. The methods of this class are for manipulating the Leach-Salz variant, although the constructors allow the creation of any variant of UUID (described below). There are four different basic types of UUIDs: time-based, DCE security, name-based, and randomly generated UUIDs. These types have a version value of 1, 2, 3 and 4, respectively.

Used to create session-id in web application. It is also used to create a transaction id. It extends Object class. It implements Serializable and Comparable interfaces.

Now let's go to implementation:-

use java.util.UUID package

UUID uniqId = UUID.randomUUID();

every time you'll use it and you'll get a random ID for your Employee.

Deepak Singh
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-1

Usually ID is a not a visible argument. Simple way, if are you use datetime based id. Example:

long id = System.currentTimeMillis();
axtros
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    Note that this does not ensure uniqueness. Even if we factor out parallelism, the current system time can drift and can be corrected by external factors like a sync via internet. Resulting in the same time coming out of this method again. – Zabuzard Jan 29 '20 at 15:29