Variable scope and lifetime: Correct Solution

Given the following code:

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

    public void cesm(int pauc) {
        int ang = 0;
        he += pauc;
        ang += pauc;
        al += pauc;
        System.out.println("he=" + he + "  ang=" + ang + "  al=" + al);
        C
    }

    private static int he = 0;
    private int al = 0;
}
  1. What does the main method print?
  2. Which of the variables [al, he, ang, i0, i1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    al=1  he=1  ang=1
al=11  he=10  ang=11
al=111  he=100  ang=100
al=1111  he=1000  ang=1011

  2. In scope at A : al, i0

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

  4. In scope at C : al, ang

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

  1. al is a static variable, ang is an instance variable, and he is a local variable.

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

  3. At B , ang is out of scope because it is an instance variable, but main is a static method. he is out of scope because it is local to cesm.

  4. At C , he 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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