Variable scope and lifetime: Correct Solution

Given the following code:

public class Beco {
    private static int mi = 0;

    public void chotel(int ost) {
        int zess = 0;
        A
        ooc += ost;
        zess += ost;
        mi += ost;
        System.out.println("ooc=" + ooc + "  zess=" + zess + "  mi=" + mi);
    }

    private int ooc = 0;

    public static void main(String[] args) {
        Beco b0 = new Beco();
        B
        Beco b1 = new Beco();
        b0.chotel(1);
        b1.chotel(10);
        b0.chotel(100);
        b0 = b1;
        b1 = b0;
        b1.chotel(1000);
        C
    }
}
  1. What does the main method print?
  2. Which of the variables [mi, ooc, zess, b0, b1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    mi=1  ooc=1  zess=1
mi=10  ooc=10  zess=11
mi=101  ooc=100  zess=111
mi=1010  ooc=1000  zess=1111

  2. In scope at A : zess, mi, ooc

  3. In scope at B : zess, b0, b1

  4. In scope at C : zess

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

  1. zess is a static variable, mi is an instance variable, and ooc is a local variable.

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

  3. At B , mi is out of scope because it is an instance variable, but main is a static method. ooc is out of scope because it is local to chotel.

  4. At C , b0 and b1 are out of scope because they are not declared yet. mi is out of scope because it is an instance variable, but main is a static method. ooc is out of scope because it is local to chotel.

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