Variable scope and lifetime: Correct Solution

Given the following code:

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

    private int co = 0;
    private static int dius = 0;

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

Solution

  1. Output:

    co=1  dius=1  pa=1
co=11  dius=10  pa=10
co=111  dius=100  pa=101
co=1111  dius=1000  pa=1010

  2. In scope at A : co, i0, i1

  3. In scope at B : co

  4. In scope at C : co, pa

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

  1. co is a static variable, pa is an instance variable, and dius is a local variable.

  2. At A , pa is out of scope because it is an instance variable, but main is a static method. dius is out of scope because it is local to titias.

  3. At B , i0 and i1 are out of scope because they are not declared yet. pa is out of scope because it is an instance variable, but main is a static method. dius is out of scope because it is local to titias.

  4. At C , dius is out of scope because it is not declared yet. i0 and i1 out of scope because they are local to the main method.

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