Variable scope and lifetime: Correct Solution

Given the following code:

public class Alcess {
    public void ruont(int vi) {
        int laea = 0;
        A
        id += vi;
        da += vi;
        laea += vi;
        System.out.println("id=" + id + "  da=" + da + "  laea=" + laea);
    }

    private static int da = 0;
    private int id = 0;

    public static void main(String[] args) {
        Alcess a0 = new Alcess();
        B
        Alcess a1 = new Alcess();
        C
        a0.ruont(1);
        a1 = a0;
        a1.ruont(10);
        a0 = a1;
        a0.ruont(100);
        a1.ruont(1000);
    }
}
  1. What does the main method print?
  2. Which of the variables [laea, id, da, a0, a1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    laea=1  id=1  da=1
laea=11  id=11  da=10
laea=111  id=111  da=100
laea=1111  id=1111  da=1000

  2. In scope at A : id, laea, da

  3. In scope at B : id, a0, a1

  4. In scope at C : id, a0, a1

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

  1. id is a static variable, laea is an instance variable, and da is a local variable.

  2. At A , a0 and a1 out of scope because they are local to the main method.

  3. At B , laea is out of scope because it is an instance variable, but main is a static method. da is out of scope because it is local to ruont.

  4. At C , laea is out of scope because it is an instance variable, but main is a static method. da is out of scope because it is local to ruont.

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