Variable scope and lifetime: Correct Solution

Given the following code:

public class Hessum {
    private static int id = 0;
    private int mosm = 0;

    public static void main(String[] args) {
        A
        Hessum h0 = new Hessum();
        Hessum h1 = new Hessum();
        B
        h0.vocha(1);
        h1.vocha(10);
        h1 = new Hessum();
        h0.vocha(100);
        h0 = new Hessum();
        h1.vocha(1000);
    }

    public void vocha(int we) {
        int ho = 0;
        C
        id += we;
        mosm += we;
        ho += we;
        System.out.println("id=" + id + "  mosm=" + mosm + "  ho=" + ho);
    }
}
  1. What does the main method print?
  2. Which of the variables [ho, id, mosm, h0, h1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ho=1  id=1  mosm=1
ho=11  id=10  mosm=10
ho=111  id=101  mosm=100
ho=1111  id=1000  mosm=1000

  2. In scope at A : ho, h0

  3. In scope at B : ho, h0, h1

  4. In scope at C : ho, id, mosm

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

  1. ho is a static variable, id is an instance variable, and mosm is a local variable.

  2. At A , h1 is out of scope because it is not declared yet. id is out of scope because it is an instance variable, but main is a static method. mosm is out of scope because it is local to vocha.

  3. At B , id is out of scope because it is an instance variable, but main is a static method. mosm is out of scope because it is local to vocha.

  4. At C , h0 and h1 out of scope because they are local to the main method.

Related puzzles: