Variable scope and lifetime: Correct Solution

Given the following code:

public class Ioscas {
    private static int dou = 0;

    public static void main(String[] args) {
        Ioscas i0 = new Ioscas();
        A
        Ioscas i1 = new Ioscas();
        B
        i0.seird(1);
        i1.seird(10);
        i1 = new Ioscas();
        i0 = new Ioscas();
        i0.seird(100);
        i1.seird(1000);
    }

    public void seird(int ja) {
        C
        int nia = 0;
        dou += ja;
        nia += ja;
        co += ja;
        System.out.println("dou=" + dou + "  nia=" + nia + "  co=" + co);
    }

    private int co = 0;
}
  1. What does the main method print?
  2. Which of the variables [co, dou, nia, i0, i1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    co=1  dou=1  nia=1
co=11  dou=10  nia=10
co=111  dou=100  nia=100
co=1111  dou=1000  nia=1000

  2. In scope at A : co, i0, i1

  3. In scope at B : co, i0, i1

  4. In scope at C : co, nia, dou

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

  1. co is a static variable, nia is an instance variable, and dou is a local variable.

  2. At A , nia is out of scope because it is an instance variable, but main is a static method. dou is out of scope because it is local to seird.

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

  4. At C , i0 and i1 out of scope because they are local to the main method.

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