How can I assign a unique sequential number to each instance of a class?

Question

I have two classes:

public class Worker{

  String name;

  private static int count=0;

  public Worker(String N){

     name=N;
     count++;
  }

  public String numberOfTime(){
      return name +", "+ count; 
  }
}

public class counting{

   public static void main(String[]args){
       Worker worker1 = new Worker("Jack");

       Worker worker2 = new Worker("John");

       System.out.println(worker1.numberOfTime());

       System.out.println(worker2.numberOfTime());
   }
}

While I want to get (Jack, 1) and (John, 2) and so on, it prints (Jack, 2) and (John, 2).

Can anyone explain me how to change this?

Thanks.

I want to give each worker a number. The first worker would be number 1, while the last one would be number n. Here however it gives me the number of time the method has been called ( always i). — le zaza, May 08 '17 at 13:03
I think you need to change the title of this question as it is completely misleading. — Steve Smith, May 08 '17 at 13:06
The output you're trying to print makes not sense, please explain what are you trying to achieve. — Maroun, May 08 '17 at 13:10
Rename your variable and method names, because they are missleading. also read about naming conventions. Class names should start with uppercase character — Jens, May 08 '17 at 13:50

Mostafa El-Messiry · Accepted Answer · 2017-05-08T13:07:13.730

3

public class Worker{

  String name;
  int number;

  private static int totalCount=0;


  public Worker(String N){

     name=N;
     totalCount++;
     number = totalCount;
  }

  public String numberOfTime(){
      return name +", "+ number; 
  }
}

Try this

You are not assigning a number to the instances, Their total count should be separate from the number assigned to every instance

edited May 08 '17 at 13:07

answered May 08 '17 at 13:05

Mostafa El-Messiry

380
1
14

typo :), Fixed it – Mostafa El-Messiry May 08 '17 at 13:07
1

You could declare number as `int number = totalCount++;` – AxelH May 08 '17 at 13:09
2

@MostafaEl-Messiry don't ask specificly for your answer to be accepted but remember OP to mark the most fitted one ;) – AxelH May 08 '17 at 13:21
2

@AxelH Hehe. [You might find this a good read](http://stackoverflow.com/questions/25168062/why-is-i-not-atomic) – Michael May 08 '17 at 13:24

Michel_T. · Answer 2 · 2017-05-08T13:22:15.820

0

If you want to set an ID to each Worker, you should so something like this:

public class Worker{

  String name;

  private static int count=0;

  private int id = ++count;

  public Worker(String N){
     name=N;
  }

  public String numberOfTime(){
      return name +", "+ id; 
  }
}

edited May 08 '17 at 13:22

answered May 08 '17 at 13:07

Michel_T.

2,741
5
21
31

Jens · Answer 3 · 2017-05-08T13:31:42.853

Best way for me is to introduce an IdGenerator as an extra class.

public class IdGenerator {

    private static int id =1;

    public static int newId(){
        return id++;
    }
}

and Change your Worker class to:

public class Worker{

  String name;

  private  int id=0;

  public Worker(String n){

     name=n;
     id = IdGenerator.newId();
  }

  public String numberOfTime(){
      return name +", "+ id; 
  }
}

It is better OO design than integrating the Counter in the object itself.

How can I assign a unique sequential number to each instance of a class?

3 Answers3