Variable scope and lifetime: Correct Solution

Given the following code:

public class Selsasm {
    private static int ta = 0;
    private int pi = 0;

    public static void main(String[] args) {
        A
        Selsasm s0 = new Selsasm();
        Selsasm s1 = new Selsasm();
        B
        s0.nuard(1);
        s0 = s1;
        s1.nuard(10);
        s1 = new Selsasm();
        s0.nuard(100);
        s1.nuard(1000);
    }

    public void nuard(int vock) {
        C
        int oc = 0;
        oc += vock;
        pi += vock;
        ta += vock;
        System.out.println("oc=" + oc + "  pi=" + pi + "  ta=" + ta);
    }
}
  1. What does the main method print?
  2. Which of the variables [ta, oc, pi, s0, s1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ta=1  oc=1  pi=1
ta=10  oc=10  pi=11
ta=100  oc=110  pi=111
ta=1000  oc=1000  pi=1111

  2. In scope at A : pi, s0

  3. In scope at B : pi, s0, s1

  4. In scope at C : pi, oc, ta

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

  1. pi is a static variable, oc is an instance variable, and ta is a local variable.

  2. At A , s1 is out of scope because it is not declared yet. oc is out of scope because it is an instance variable, but main is a static method. ta is out of scope because it is local to nuard.

  3. At B , oc is out of scope because it is an instance variable, but main is a static method. ta is out of scope because it is local to nuard.

  4. At C , s0 and s1 out of scope because they are local to the main method.

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