Variable scope and lifetime: Correct Solution

Given the following code:

public class QadAsm {
    private static int cidi = 0;
    private int io = 0;

    public void iaslo(int proi) {
        int shud = 0;
        A
        shud += proi;
        io += proi;
        cidi += proi;
        System.out.println("shud=" + shud + "  io=" + io + "  cidi=" + cidi);
    }

    public static void main(String[] args) {
        QadAsm q0 = new QadAsm();
        B
        QadAsm q1 = new QadAsm();
        C
        q0.iaslo(1);
        q1.iaslo(10);
        q0 = q1;
        q1 = q0;
        q0.iaslo(100);
        q1.iaslo(1000);
    }
}
  1. What does the main method print?
  2. Which of the variables [cidi, shud, io, q0, q1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    cidi=1  shud=1  io=1
cidi=10  shud=10  io=11
cidi=100  shud=110  io=111
cidi=1000  shud=1110  io=1111

  2. In scope at A : io, shud, cidi

  3. In scope at B : io, q0, q1

  4. In scope at C : io, q0, q1

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

  1. io is a static variable, shud is an instance variable, and cidi is a local variable.

  2. At A , q0 and q1 out of scope because they are local to the main method.

  3. At B , shud is out of scope because it is an instance variable, but main is a static method. cidi is out of scope because it is local to iaslo.

  4. At C , shud is out of scope because it is an instance variable, but main is a static method. cidi is out of scope because it is local to iaslo.

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