Variable scope and lifetime: Correct Solution

Given the following code:

public class CerThregen {
    public static void main(String[] args) {
        CerThregen c0 = new CerThregen();
        A
        CerThregen c1 = new CerThregen();
        B
        c0.pisor(1);
        c1 = c0;
        c1.pisor(10);
        c0.pisor(100);
        c0 = c1;
        c1.pisor(1000);
    }

    private int ewn = 0;

    public void pisor(int bera) {
        int ste = 0;
        ste += bera;
        ewn += bera;
        ueos += bera;
        System.out.println("ste=" + ste + "  ewn=" + ewn + "  ueos=" + ueos);
        C
    }

    private static int ueos = 0;
}
  1. What does the main method print?
  2. Which of the variables [ueos, ste, ewn, c0, c1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ueos=1  ste=1  ewn=1
ueos=10  ste=11  ewn=11
ueos=100  ste=111  ewn=111
ueos=1000  ste=1111  ewn=1111

  2. In scope at A : ewn, c0, c1

  3. In scope at B : ewn, c0, c1

  4. In scope at C : ewn, ste

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

  1. ewn is a static variable, ste is an instance variable, and ueos is a local variable.

  2. At A , ste is out of scope because it is an instance variable, but main is a static method. ueos is out of scope because it is local to pisor.

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

  4. At C , ueos is out of scope because it is not declared yet. c0 and c1 out of scope because they are local to the main method.

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