Variable scope and lifetime: Correct Solution

Given the following code:

public class Prisstheat {
    public static void main(String[] args) {
        A
        Prisstheat p0 = new Prisstheat();
        Prisstheat p1 = new Prisstheat();
        B
        p0.hickhi(1);
        p0 = p1;
        p1.hickhi(10);
        p1 = new Prisstheat();
        p0.hickhi(100);
        p1.hickhi(1000);
    }

    private static int dros = 0;
    private int idso = 0;

    public void hickhi(int choi) {
        C
        int pha = 0;
        idso += choi;
        pha += choi;
        dros += choi;
        System.out.println("idso=" + idso + "  pha=" + pha + "  dros=" + dros);
    }
}
  1. What does the main method print?
  2. Which of the variables [dros, idso, pha, p0, p1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    dros=1  idso=1  pha=1
dros=10  idso=10  pha=11
dros=110  idso=100  pha=111
dros=1000  idso=1000  pha=1111

  2. In scope at A : pha, p0

  3. In scope at B : pha, p0, p1

  4. In scope at C : pha, dros, idso

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

  1. pha is a static variable, dros is an instance variable, and idso is a local variable.

  2. At A , p1 is out of scope because it is not declared yet. dros is out of scope because it is an instance variable, but main is a static method. idso is out of scope because it is local to hickhi.

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

  4. At C , p0 and p1 out of scope because they are local to the main method.

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