Variable scope and lifetime: Correct Solution

Given the following code:

public class Jefun {
    public static void main(String[] args) {
        A
        Jefun j0 = new Jefun();
        Jefun j1 = new Jefun();
        B
        j0.nousm(1);
        j0 = new Jefun();
        j1.nousm(10);
        j1 = new Jefun();
        j0.nousm(100);
        j1.nousm(1000);
    }

    private int si = 0;

    public void nousm(int tro) {
        int e = 0;
        C
        e += tro;
        blir += tro;
        si += tro;
        System.out.println("e=" + e + "  blir=" + blir + "  si=" + si);
    }

    private static int blir = 0;
}
  1. What does the main method print?
  2. Which of the variables [si, e, blir, j0, j1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    si=1  e=1  blir=1
si=10  e=11  blir=10
si=100  e=111  blir=100
si=1000  e=1111  blir=1000

  2. In scope at A : e, j0

  3. In scope at B : e, j0, j1

  4. In scope at C : e, blir, si

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

  1. e is a static variable, blir is an instance variable, and si is a local variable.

  2. At A , j1 is out of scope because it is not declared yet. blir is out of scope because it is an instance variable, but main is a static method. si is out of scope because it is local to nousm.

  3. At B , blir is out of scope because it is an instance variable, but main is a static method. si is out of scope because it is local to nousm.

  4. At C , j0 and j1 out of scope because they are local to the main method.

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