Variable scope and lifetime: Correct Solution

Given the following code:

public class Stofa {
    public void dubal(int oss) {
        A
        int qad = 0;
        ziid += oss;
        qad += oss;
        e += oss;
        System.out.println("ziid=" + ziid + "  qad=" + qad + "  e=" + e);
    }

    public static void main(String[] args) {
        Stofa s0 = new Stofa();
        B
        Stofa s1 = new Stofa();
        s0.dubal(1);
        s1.dubal(10);
        s1 = s0;
        s0 = s1;
        s0.dubal(100);
        s1.dubal(1000);
        C
    }

    private static int ziid = 0;
    private int e = 0;
}
  1. What does the main method print?
  2. Which of the variables [e, ziid, qad, s0, s1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    e=1  ziid=1  qad=1
e=11  ziid=10  qad=10
e=111  ziid=100  qad=101
e=1111  ziid=1000  qad=1101

  2. In scope at A : e, qad, ziid

  3. In scope at B : e, s0, s1

  4. In scope at C : e

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

  1. e is a static variable, qad is an instance variable, and ziid is a local variable.

  2. At A , s0 and s1 out of scope because they are local to the main method.

  3. At B , qad is out of scope because it is an instance variable, but main is a static method. ziid is out of scope because it is local to dubal.

  4. At C , s0 and s1 are out of scope because they are not declared yet. qad is out of scope because it is an instance variable, but main is a static method. ziid is out of scope because it is local to dubal.

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