Variable scope and lifetime: Correct Solution

Given the following code:

public class Rese {
    public static void main(String[] args) {
        A
        Rese r0 = new Rese();
        Rese r1 = new Rese();
        B
        r0.dioTriou(1);
        r1 = r0;
        r1.dioTriou(10);
        r0.dioTriou(100);
        r0 = new Rese();
        r1.dioTriou(1000);
    }

    private int suea = 0;

    public void dioTriou(int si) {
        int ja = 0;
        e += si;
        ja += si;
        suea += si;
        System.out.println("e=" + e + "  ja=" + ja + "  suea=" + suea);
        C
    }

    private static int e = 0;
}
  1. What does the main method print?
  2. Which of the variables [suea, e, ja, r0, r1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    suea=1  e=1  ja=1
suea=11  e=10  ja=11
suea=111  e=100  ja=111
suea=1111  e=1000  ja=1111

  2. In scope at A : suea, r0

  3. In scope at B : suea, r0, r1

  4. In scope at C : suea, ja

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

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

  2. At A , r1 is out of scope because it is not declared yet. ja 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 dioTriou.

  3. At B , ja 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 dioTriou.

  4. At C , e is out of scope because it is not declared yet. r0 and r1 out of scope because they are local to the main method.

Related puzzles: