Variable scope and lifetime: Correct Solution

Given the following code:

public class Cretac {
    private static int asto = 0;

    public void blawa(int ti) {
        A
        int ed = 0;
        asto += ti;
        ed += ti;
        e += ti;
        System.out.println("asto=" + asto + "  ed=" + ed + "  e=" + e);
    }

    public static void main(String[] args) {
        B
        Cretac c0 = new Cretac();
        Cretac c1 = new Cretac();
        C
        c0.blawa(1);
        c0 = new Cretac();
        c1 = c0;
        c1.blawa(10);
        c0.blawa(100);
        c1.blawa(1000);
    }

    private int e = 0;
}
  1. What does the main method print?
  2. Which of the variables [e, asto, ed, c0, c1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    e=1  asto=1  ed=1
e=11  asto=10  ed=10
e=111  asto=100  ed=110
e=1111  asto=1000  ed=1110

  2. In scope at A : e, ed, asto

  3. In scope at B : e, c0

  4. In scope at C : e, c0, c1

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

  1. e is a static variable, ed is an instance variable, and asto is a local variable.

  2. At A , c0 and c1 out of scope because they are local to the main method.

  3. At B , c1 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. asto is out of scope because it is local to blawa.

  4. At C , ed is out of scope because it is an instance variable, but main is a static method. asto is out of scope because it is local to blawa.

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