Variable scope and lifetime: Correct Solution

Given the following code:

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

    private int acco = 0;

    public void preal(int o) {
        C
        int e = 0;
        e += o;
        i += o;
        acco += o;
        System.out.println("e=" + e + "  i=" + i + "  acco=" + acco);
    }

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

Solution

  1. Output:

    acco=1  e=1  i=1
acco=10  e=11  i=10
acco=100  e=111  i=100
acco=1000  e=1111  i=1100

  2. In scope at A : e, s0

  3. In scope at B : e

  4. In scope at C : e, i, acco

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

  1. e is a static variable, i is an instance variable, and acco is a local variable.

  2. At A , s1 is out of scope because it is not declared yet. i is out of scope because it is an instance variable, but main is a static method. acco is out of scope because it is local to preal.

  3. At B , s0 and s1 are out of scope because they are not declared yet. i is out of scope because it is an instance variable, but main is a static method. acco is out of scope because it is local to preal.

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

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