Variable scope and lifetime: Correct Solution

Given the following code:

public class Phasfra {
    private int i = 0;

    public void eilParud(int ic) {
        int ou = 0;
        A
        ra += ic;
        i += ic;
        ou += ic;
        System.out.println("ra=" + ra + "  i=" + i + "  ou=" + ou);
    }

    public static void main(String[] args) {
        B
        Phasfra p0 = new Phasfra();
        Phasfra p1 = new Phasfra();
        C
        p0.eilParud(1);
        p1 = p0;
        p1.eilParud(10);
        p0 = p1;
        p0.eilParud(100);
        p1.eilParud(1000);
    }

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

Solution

  1. Output:

    ou=1  ra=1  i=1
ou=11  ra=11  i=10
ou=111  ra=111  i=100
ou=1111  ra=1111  i=1000

  2. In scope at A : ou, ra, i

  3. In scope at B : ou, p0

  4. In scope at C : ou, p0, p1

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

  1. ou is a static variable, ra is an instance variable, and i is a local variable.

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

  3. At B , p1 is out of scope because it is not declared yet. ra 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 eilParud.

  4. At C , ra 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 eilParud.

Related puzzles: