Variable scope and lifetime: Correct Solution

Given the following code:

public class Diount {
    private static int i = 0;
    private int ris = 0;

    public void ilnuan(int e) {
        int nec = 0;
        ris += e;
        i += e;
        nec += e;
        System.out.println("ris=" + ris + "  i=" + i + "  nec=" + nec);
        A
    }

    public static void main(String[] args) {
        Diount d0 = new Diount();
        B
        Diount d1 = new Diount();
        d0.ilnuan(1);
        d1.ilnuan(10);
        d0 = d1;
        d0.ilnuan(100);
        d1 = new Diount();
        d1.ilnuan(1000);
        C
    }
}
  1. What does the main method print?
  2. Which of the variables [nec, ris, i, d0, d1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    nec=1  ris=1  i=1
nec=10  ris=11  i=10
nec=110  ris=111  i=100
nec=1000  ris=1111  i=1000

  2. In scope at A : ris, nec

  3. In scope at B : ris, d0, d1

  4. In scope at C : ris

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

  1. ris is a static variable, nec is an instance variable, and i is a local variable.

  2. At A , i is out of scope because it is not declared yet. d0 and d1 out of scope because they are local to the main method.

  3. At B , nec is out of scope because it is an instance variable, but main is a static method. i is out of scope because it is local to ilnuan.

  4. At C , d0 and d1 are out of scope because they are not declared yet. nec is out of scope because it is an instance variable, but main is a static method. i is out of scope because it is local to ilnuan.

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