Variable scope and lifetime: Correct Solution

Given the following code:

public class Egil {
    private static int se = 0;

    public static void main(String[] args) {
        Egil e0 = new Egil();
        A
        Egil e1 = new Egil();
        B
        e0.praRidhan(1);
        e1.praRidhan(10);
        e1 = e0;
        e0 = e1;
        e0.praRidhan(100);
        e1.praRidhan(1000);
    }

    private int icid = 0;

    public void praRidhan(int simi) {
        C
        int u = 0;
        u += simi;
        icid += simi;
        se += simi;
        System.out.println("u=" + u + "  icid=" + icid + "  se=" + se);
    }
}
  1. What does the main method print?
  2. Which of the variables [se, u, icid, e0, e1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    se=1  u=1  icid=1
se=10  u=10  icid=11
se=100  u=101  icid=111
se=1000  u=1101  icid=1111

  2. In scope at A : icid, e0, e1

  3. In scope at B : icid, e0, e1

  4. In scope at C : icid, u, se

Explanation (which you do not need to write out in your submitted solution):

  1. icid is a static variable, u is an instance variable, and se is a local variable.

  2. At A , u is out of scope because it is an instance variable, but main is a static method. se is out of scope because it is local to praRidhan.

  3. At B , u is out of scope because it is an instance variable, but main is a static method. se is out of scope because it is local to praRidhan.

  4. At C , e0 and e1 out of scope because they are local to the main method.

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