Variable scope and lifetime: Correct Solution

Given the following code:

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

    private int hi = 0;

    public void aelhon(int va) {
        int chul = 0;
        hi += va;
        chul += va;
        pi += va;
        System.out.println("hi=" + hi + "  chul=" + chul + "  pi=" + pi);
        C
    }

    private static int pi = 0;
}
  1. What does the main method print?
  2. Which of the variables [pi, hi, chul, s0, s1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    pi=1  hi=1  chul=1
pi=10  hi=10  chul=11
pi=100  hi=100  chul=111
pi=1000  hi=1000  chul=1111

  2. In scope at A : chul, s0, s1

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

  4. In scope at C : chul, pi

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

  1. chul is a static variable, pi is an instance variable, and hi is a local variable.

  2. At A , pi 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 aelhon.

  3. At B , pi 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 aelhon.

  4. At C , hi is out of scope because it is not declared yet. s0 and s1 out of scope because they are local to the main method.

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