Variable scope and lifetime: Correct Solution

Given the following code:

public class Shissbi {
    private int id = 0;

    public void ionad(int es) {
        int o = 0;
        id += es;
        o += es;
        heus += es;
        System.out.println("id=" + id + "  o=" + o + "  heus=" + heus);
        A
    }

    public static void main(String[] args) {
        B
        Shissbi s0 = new Shissbi();
        Shissbi s1 = new Shissbi();
        C
        s0.ionad(1);
        s1.ionad(10);
        s0 = new Shissbi();
        s1 = new Shissbi();
        s0.ionad(100);
        s1.ionad(1000);
    }

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

Solution

  1. Output:

    heus=1  id=1  o=1
heus=10  id=10  o=11
heus=100  id=100  o=111
heus=1000  id=1000  o=1111

  2. In scope at A : o, heus

  3. In scope at B : o, s0

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

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

  1. o is a static variable, heus is an instance variable, and id is a local variable.

  2. At A , id is out of scope because it is not declared yet. 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. heus is out of scope because it is an instance variable, but main is a static method. id is out of scope because it is local to ionad.

  4. At C , heus is out of scope because it is an instance variable, but main is a static method. id is out of scope because it is local to ionad.

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