Variable scope and lifetime: Correct Solution

Given the following code:

public class Sekal {
    public static void main(String[] args) {
        A
        Sekal s0 = new Sekal();
        Sekal s1 = new Sekal();
        B
        s0.cirhi(1);
        s1.cirhi(10);
        s0.cirhi(100);
        s1 = s0;
        s0 = new Sekal();
        s1.cirhi(1000);
    }

    private int se = 0;
    private static int ed = 0;

    public void cirhi(int i) {
        int po = 0;
        se += i;
        po += i;
        ed += i;
        System.out.println("se=" + se + "  po=" + po + "  ed=" + ed);
        C
    }
}
  1. What does the main method print?
  2. Which of the variables [ed, se, po, s0, s1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ed=1  se=1  po=1
ed=10  se=10  po=11
ed=101  se=100  po=111
ed=1101  se=1000  po=1111

  2. In scope at A : po, s0

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

  4. In scope at C : po, ed

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

  1. po is a static variable, ed is an instance variable, and se is a local variable.

  2. At A , s1 is out of scope because it is not declared yet. ed 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 cirhi.

  3. At B , ed 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 cirhi.

  4. At C , se is out of scope because it is not declared yet. s0 and s1 out of scope because they are local to the main method.

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