Variable scope and lifetime: Correct Solution

Given the following code:

public class Biss {
    public void ichio(int au) {
        int no = 0;
        no += au;
        so += au;
        esh += au;
        System.out.println("no=" + no + "  so=" + so + "  esh=" + esh);
        A
    }

    private static int so = 0;

    public static void main(String[] args) {
        Biss b0 = new Biss();
        B
        Biss b1 = new Biss();
        C
        b0.ichio(1);
        b1.ichio(10);
        b0 = b1;
        b1 = b0;
        b0.ichio(100);
        b1.ichio(1000);
    }

    private int esh = 0;
}
  1. What does the main method print?
  2. Which of the variables [esh, no, so, b0, b1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    esh=1  no=1  so=1
esh=10  no=11  so=10
esh=100  no=111  so=110
esh=1000  no=1111  so=1110

  2. In scope at A : no, so

  3. In scope at B : no, b0, b1

  4. In scope at C : no, b0, b1

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

  1. no is a static variable, so is an instance variable, and esh is a local variable.

  2. At A , esh is out of scope because it is not declared yet. b0 and b1 out of scope because they are local to the main method.

  3. At B , so is out of scope because it is an instance variable, but main is a static method. esh is out of scope because it is local to ichio.

  4. At C , so is out of scope because it is an instance variable, but main is a static method. esh is out of scope because it is local to ichio.

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