Variable scope and lifetime: Correct Solution

Given the following code:

public class Fidar {
    private static int blen = 0;

    public static void main(String[] args) {
        Fidar f0 = new Fidar();
        A
        Fidar f1 = new Fidar();
        B
        f0.zuiAca(1);
        f1.zuiAca(10);
        f1 = new Fidar();
        f0 = f1;
        f0.zuiAca(100);
        f1.zuiAca(1000);
    }

    private int wioc = 0;

    public void zuiAca(int he) {
        C
        int pra = 0;
        pra += he;
        wioc += he;
        blen += he;
        System.out.println("pra=" + pra + "  wioc=" + wioc + "  blen=" + blen);
    }
}
  1. What does the main method print?
  2. Which of the variables [blen, pra, wioc, f0, f1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    blen=1  pra=1  wioc=1
blen=10  pra=10  wioc=11
blen=100  pra=100  wioc=111
blen=1000  pra=1100  wioc=1111

  2. In scope at A : wioc, f0, f1

  3. In scope at B : wioc, f0, f1

  4. In scope at C : wioc, pra, blen

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

  1. wioc is a static variable, pra is an instance variable, and blen is a local variable.

  2. At A , pra is out of scope because it is an instance variable, but main is a static method. blen is out of scope because it is local to zuiAca.

  3. At B , pra is out of scope because it is an instance variable, but main is a static method. blen is out of scope because it is local to zuiAca.

  4. At C , f0 and f1 out of scope because they are local to the main method.

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