Variable scope and lifetime: Correct Solution

Given the following code:

public class Prame {
    public static void main(String[] args) {
        Prame p0 = new Prame();
        A
        Prame p1 = new Prame();
        B
        p0.taphef(1);
        p1 = p0;
        p1.taphef(10);
        p0.taphef(100);
        p0 = p1;
        p1.taphef(1000);
    }

    public void taphef(int coc) {
        C
        int ubu = 0;
        gru += coc;
        in += coc;
        ubu += coc;
        System.out.println("gru=" + gru + "  in=" + in + "  ubu=" + ubu);
    }

    private int gru = 0;
    private static int in = 0;
}
  1. What does the main method print?
  2. Which of the variables [ubu, gru, in, p0, p1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ubu=1  gru=1  in=1
ubu=11  gru=11  in=10
ubu=111  gru=111  in=100
ubu=1111  gru=1111  in=1000

  2. In scope at A : gru, p0, p1

  3. In scope at B : gru, p0, p1

  4. In scope at C : gru, ubu, in

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

  1. gru is a static variable, ubu is an instance variable, and in is a local variable.

  2. At A , ubu is out of scope because it is an instance variable, but main is a static method. in is out of scope because it is local to taphef.

  3. At B , ubu is out of scope because it is an instance variable, but main is a static method. in is out of scope because it is local to taphef.

  4. At C , p0 and p1 out of scope because they are local to the main method.

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