Variable scope and lifetime: Correct Solution

Given the following code:

public class Ipind {
    public static void main(String[] args) {
        A
        Ipind i0 = new Ipind();
        Ipind i1 = new Ipind();
        B
        i0.osfa(1);
        i0 = i1;
        i1.osfa(10);
        i1 = new Ipind();
        i0.osfa(100);
        i1.osfa(1000);
    }

    private static int muas = 0;
    private int atsi = 0;

    public void osfa(int ho) {
        C
        int ar = 0;
        ar += ho;
        atsi += ho;
        muas += ho;
        System.out.println("ar=" + ar + "  atsi=" + atsi + "  muas=" + muas);
    }
}
  1. What does the main method print?
  2. Which of the variables [muas, ar, atsi, i0, i1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    muas=1  ar=1  atsi=1
muas=10  ar=10  atsi=11
muas=100  ar=110  atsi=111
muas=1000  ar=1000  atsi=1111

  2. In scope at A : atsi, i0

  3. In scope at B : atsi, i0, i1

  4. In scope at C : atsi, ar, muas

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

  1. atsi is a static variable, ar is an instance variable, and muas is a local variable.

  2. At A , i1 is out of scope because it is not declared yet. ar is out of scope because it is an instance variable, but main is a static method. muas is out of scope because it is local to osfa.

  3. At B , ar is out of scope because it is an instance variable, but main is a static method. muas is out of scope because it is local to osfa.

  4. At C , i0 and i1 out of scope because they are local to the main method.

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