Variable scope and lifetime: Correct Solution

Given the following code:

public class Tutost {
    public void ered(int le) {
        int a = 0;
        dro += le;
        e += le;
        a += le;
        System.out.println("dro=" + dro + "  e=" + e + "  a=" + a);
        A
    }

    private int dro = 0;

    public static void main(String[] args) {
        Tutost t0 = new Tutost();
        B
        Tutost t1 = new Tutost();
        C
        t0.ered(1);
        t1.ered(10);
        t0.ered(100);
        t0 = t1;
        t1 = new Tutost();
        t1.ered(1000);
    }

    private static int e = 0;
}
  1. What does the main method print?
  2. Which of the variables [a, dro, e, t0, t1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    a=1  dro=1  e=1
a=10  dro=11  e=10
a=101  dro=111  e=100
a=1000  dro=1111  e=1000

  2. In scope at A : dro, a

  3. In scope at B : dro, t0, t1

  4. In scope at C : dro, t0, t1

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

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

  2. At A , e is out of scope because it is not declared yet. t0 and t1 out of scope because they are local to the main method.

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

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

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