Variable scope and lifetime: Correct Solution

Given the following code:

public class Seill {
    public void qadont(int ef) {
        int om = 0;
        A
        om += ef;
        si += ef;
        ia += ef;
        System.out.println("om=" + om + "  si=" + si + "  ia=" + ia);
    }

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

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

Solution

  1. Output:

    ia=1  om=1  si=1
ia=10  om=11  si=11
ia=100  om=111  si=111
ia=1000  om=1111  si=1111

  2. In scope at A : om, si, ia

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

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

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

  1. om is a static variable, si is an instance variable, and ia is a local variable.

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

  3. At B , si is out of scope because it is an instance variable, but main is a static method. ia is out of scope because it is local to qadont.

  4. At C , si is out of scope because it is an instance variable, but main is a static method. ia is out of scope because it is local to qadont.

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