Question

I wanted the ID was 1,2,3,4 each new name, ie

ID – Name – Age

1 – Paul – 60

2 – Regis – 25

3 – Ana – 20

automatic ID

static void register(ArrayList mylist) {
        int i = 1;
        Scanner in = new Scanner(System.in);
        Peoples p = new Peoples();
//        System.out.print("ID: ");
//        p.ID = in.nextInt();
        p.ID = i;
        i++;
        in.nextLine();
        System.out.print("Name: ");
        p.name = in.nextLine();
        System.out.print("Age: ");
        p.age = in.nextInt();
        mylist.add(p);
    }


public class Peoples {
    public int ID;
    public String name;
    public int age;
}

Answer 1

I would slightly modified the Peoples class (btw. it is a goood practice to use a singular for class names).

public class Person {
    private static int lastId;
    private int id;
    private String name;
    private int age;

    public Person() {
      id = Person.lastId++;
    }

    public void setName(String name) {
      this.name = name;
    }

    public void setAge(int age) {
      this.age = age;
    }
}