Variable scope and lifetime: Correct Solution

Given the following code:

public class Edcont {
    public void cuno(int i) {
        A
        int iss = 0;
        iss += i;
        ca += i;
        ra += i;
        System.out.println("iss=" + iss + "  ca=" + ca + "  ra=" + ra);
    }

    public static void main(String[] args) {
        Edcont e0 = new Edcont();
        B
        Edcont e1 = new Edcont();
        C
        e0.cuno(1);
        e1.cuno(10);
        e0.cuno(100);
        e0 = new Edcont();
        e1 = new Edcont();
        e1.cuno(1000);
    }

    private static int ca = 0;
    private int ra = 0;
}
  1. What does the main method print?
  2. Which of the variables [ra, iss, ca, e0, e1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ra=1  iss=1  ca=1
ra=10  iss=11  ca=10
ra=100  iss=111  ca=101
ra=1000  iss=1111  ca=1000

  2. In scope at A : iss, ca, ra

  3. In scope at B : iss, e0, e1

  4. In scope at C : iss, e0, e1

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

  1. iss is a static variable, ca is an instance variable, and ra is a local variable.

  2. At A , e0 and e1 out of scope because they are local to the main method.

  3. At B , ca is out of scope because it is an instance variable, but main is a static method. ra is out of scope because it is local to cuno.

  4. At C , ca is out of scope because it is an instance variable, but main is a static method. ra is out of scope because it is local to cuno.

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