Auto increment for transaction number (Eclipse Java)

Question

I want to get increasing value starting with 1 so that I get TK-1 all the way to TK-n.

What I've tried is:

public class Main {
addTicket();


public void addTicket() {
int a;
String ticket;
a = getA();
ticket = "TK-"+ a
System.out.println(ticket)
}

public int getA() {
    int a, b;
    a = 0;
    b = a++;
    return a;
public static void main(String[] args) {
    new Main();

}
}

Sorry it's my first time learning to code, can someone explain to me why it isn't working and what should I do to make it work ?

Thanks in advance.

Answer 1

If you need an autoincrease ID, you need a static int:

public class Ticket {
    static int ticketID = 1;


    public void addTicket() {
        int a;
        String ticket;
        a = getticketID();
        ticket = "TK-" + a;
        System.out.println(ticket);
    }
    public int getticketID () {
        return ticketID++;
    }

    public static void main(String[] args) {
        Ticket test  = new Ticket();
        test.addTicket();
        test.addTicket();
        test.addTicket();

    }
}

output:

enter image description here