Variable scope and lifetime: Correct Solution

Given the following code:

public class Murlac {
    private int i = 0;

    public static void main(String[] args) {
        A
        Murlac m0 = new Murlac();
        Murlac m1 = new Murlac();
        B
        m0.trou(1);
        m1.trou(10);
        m1 = m0;
        m0 = new Murlac();
        m0.trou(100);
        m1.trou(1000);
    }

    private static int ciac = 0;

    public void trou(int pu) {
        int ed = 0;
        C
        ciac += pu;
        i += pu;
        ed += pu;
        System.out.println("ciac=" + ciac + "  i=" + i + "  ed=" + ed);
    }
}
  1. What does the main method print?
  2. Which of the variables [ed, ciac, i, m0, m1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ed=1  ciac=1  i=1
ed=11  ciac=10  i=10
ed=111  ciac=100  i=100
ed=1111  ciac=1001  i=1000

  2. In scope at A : ed, m0

  3. In scope at B : ed, m0, m1

  4. In scope at C : ed, ciac, i

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

  1. ed is a static variable, ciac is an instance variable, and i is a local variable.

  2. At A , m1 is out of scope because it is not declared yet. ciac is out of scope because it is an instance variable, but main is a static method. i is out of scope because it is local to trou.

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

  4. At C , m0 and m1 out of scope because they are local to the main method.

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