Variable scope and lifetime: Correct Solution

Given the following code:

public class NinIdwe {
    private static int flen = 0;
    private int me = 0;

    public static void main(String[] args) {
        NinIdwe n0 = new NinIdwe();
        A
        NinIdwe n1 = new NinIdwe();
        B
        n0.emas(1);
        n1.emas(10);
        n0 = new NinIdwe();
        n1 = n0;
        n0.emas(100);
        n1.emas(1000);
    }

    public void emas(int wu) {
        int ii = 0;
        flen += wu;
        ii += wu;
        me += wu;
        System.out.println("flen=" + flen + "  ii=" + ii + "  me=" + me);
        C
    }
}
  1. What does the main method print?
  2. Which of the variables [me, flen, ii, n0, n1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    me=1  flen=1  ii=1
me=11  flen=10  ii=10
me=111  flen=100  ii=100
me=1111  flen=1000  ii=1100

  2. In scope at A : me, n0, n1

  3. In scope at B : me, n0, n1

  4. In scope at C : me, ii

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

  1. me is a static variable, ii is an instance variable, and flen is a local variable.

  2. At A , ii is out of scope because it is an instance variable, but main is a static method. flen is out of scope because it is local to emas.

  3. At B , ii is out of scope because it is an instance variable, but main is a static method. flen is out of scope because it is local to emas.

  4. At C , flen is out of scope because it is not declared yet. n0 and n1 out of scope because they are local to the main method.

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