Variable scope and lifetime: Correct Solution

Given the following code:

public class Pruck {
    private int hi = 0;
    private static int fede = 0;

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

    public void cuesbe(int re) {
        int pui = 0;
        C
        pui += re;
        fede += re;
        hi += re;
        System.out.println("pui=" + pui + "  fede=" + fede + "  hi=" + hi);
    }
}
  1. What does the main method print?
  2. Which of the variables [hi, pui, fede, p0, p1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    hi=1  pui=1  fede=1
hi=10  pui=11  fede=10
hi=100  pui=111  fede=100
hi=1000  pui=1111  fede=1100

  2. In scope at A : pui, p0

  3. In scope at B : pui

  4. In scope at C : pui, fede, hi

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

  1. pui is a static variable, fede is an instance variable, and hi is a local variable.

  2. At A , p1 is out of scope because it is not declared yet. fede is out of scope because it is an instance variable, but main is a static method. hi is out of scope because it is local to cuesbe.

  3. At B , p0 and p1 are out of scope because they are not declared yet. fede is out of scope because it is an instance variable, but main is a static method. hi is out of scope because it is local to cuesbe.

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

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