Variable scope and lifetime: Correct Solution

Given the following code:

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

    public void scid(int cu) {
        int trar = 0;
        C
        hil += cu;
        oro += cu;
        trar += cu;
        System.out.println("hil=" + hil + "  oro=" + oro + "  trar=" + trar);
    }

    private static int oro = 0;
    private int hil = 0;
}
  1. What does the main method print?
  2. Which of the variables [trar, hil, oro, n0, n1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    trar=1  hil=1  oro=1
trar=10  hil=11  oro=10
trar=110  hil=111  oro=100
trar=1000  hil=1111  oro=1000

  2. In scope at A : hil, n0

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

  4. In scope at C : hil, trar, oro

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

  1. hil is a static variable, trar is an instance variable, and oro is a local variable.

  2. At A , n1 is out of scope because it is not declared yet. trar is out of scope because it is an instance variable, but main is a static method. oro is out of scope because it is local to scid.

  3. At B , trar is out of scope because it is an instance variable, but main is a static method. oro is out of scope because it is local to scid.

  4. At C , n0 and n1 out of scope because they are local to the main method.

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