Variable scope and lifetime: Correct Solution

Given the following code:

public class BicEict {
    private int prul = 0;

    public static void main(String[] args) {
        BicEict b0 = new BicEict();
        A
        BicEict b1 = new BicEict();
        b0.osdes(1);
        b0 = b1;
        b1 = new BicEict();
        b1.osdes(10);
        b0.osdes(100);
        b1.osdes(1000);
        B
    }

    private static int sa = 0;

    public void osdes(int biil) {
        C
        int de = 0;
        de += biil;
        prul += biil;
        sa += biil;
        System.out.println("de=" + de + "  prul=" + prul + "  sa=" + sa);
    }
}
  1. What does the main method print?
  2. Which of the variables [sa, de, prul, b0, b1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    sa=1  de=1  prul=1
sa=10  de=10  prul=11
sa=100  de=100  prul=111
sa=1000  de=1010  prul=1111

  2. In scope at A : prul, b0, b1

  3. In scope at B : prul

  4. In scope at C : prul, de, sa

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

  1. prul is a static variable, de is an instance variable, and sa is a local variable.

  2. At A , de is out of scope because it is an instance variable, but main is a static method. sa is out of scope because it is local to osdes.

  3. At B , b0 and b1 are out of scope because they are not declared yet. de is out of scope because it is an instance variable, but main is a static method. sa is out of scope because it is local to osdes.

  4. At C , b0 and b1 out of scope because they are local to the main method.

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