Variable scope and lifetime: Correct Solution

Given the following code:

public class Tazo {
    private static int ophe = 0;
    private int co = 0;

    public static void main(String[] args) {
        Tazo t0 = new Tazo();
        A
        Tazo t1 = new Tazo();
        t0.siesra(1);
        t1.siesra(10);
        t1 = t0;
        t0 = new Tazo();
        t0.siesra(100);
        t1.siesra(1000);
        B
    }

    public void siesra(int esh) {
        int he = 0;
        ophe += esh;
        co += esh;
        he += esh;
        System.out.println("ophe=" + ophe + "  co=" + co + "  he=" + he);
        C
    }
}
  1. What does the main method print?
  2. Which of the variables [he, ophe, co, t0, t1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    he=1  ophe=1  co=1
he=11  ophe=10  co=10
he=111  ophe=100  co=100
he=1111  ophe=1001  co=1000

  2. In scope at A : he, t0, t1

  3. In scope at B : he

  4. In scope at C : he, ophe

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

  1. he is a static variable, ophe is an instance variable, and co is a local variable.

  2. At A , ophe is out of scope because it is an instance variable, but main is a static method. co is out of scope because it is local to siesra.

  3. At B , t0 and t1 are out of scope because they are not declared yet. ophe is out of scope because it is an instance variable, but main is a static method. co is out of scope because it is local to siesra.

  4. At C , co is out of scope because it is not declared yet. t0 and t1 out of scope because they are local to the main method.

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