Variable scope and lifetime: Correct Solution

Given the following code:

public class Scred {
    public void mienon(int iro) {
        int iot = 0;
        A
        a += iro;
        hi += iro;
        iot += iro;
        System.out.println("a=" + a + "  hi=" + hi + "  iot=" + iot);
    }

    private int a = 0;
    private static int hi = 0;

    public static void main(String[] args) {
        B
        Scred s0 = new Scred();
        Scred s1 = new Scred();
        C
        s0.mienon(1);
        s1.mienon(10);
        s1 = s0;
        s0 = new Scred();
        s0.mienon(100);
        s1.mienon(1000);
    }
}
  1. What does the main method print?
  2. Which of the variables [iot, a, hi, s0, s1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    iot=1  a=1  hi=1
iot=10  a=11  hi=10
iot=100  a=111  hi=100
iot=1001  a=1111  hi=1000

  2. In scope at A : a, iot, hi

  3. In scope at B : a, s0

  4. In scope at C : a, s0, s1

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

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

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

  3. At B , s1 is out of scope because it is not declared yet. iot 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 mienon.

  4. At C , iot 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 mienon.

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