Variable scope and lifetime: Correct Solution

Given the following code:

public class Pedint {
    private static int ewn = 0;

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

    private int prus = 0;

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

Solution

  1. Output:

    caar=1  ewn=1  prus=1
caar=11  ewn=10  prus=10
caar=111  ewn=110  prus=100
caar=1111  ewn=1000  prus=1000

  2. In scope at A : caar, p0, p1

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

  4. In scope at C : caar, ewn, prus

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

  1. caar is a static variable, ewn is an instance variable, and prus is a local variable.

  2. At A , ewn is out of scope because it is an instance variable, but main is a static method. prus is out of scope because it is local to bilOng.

  3. At B , ewn is out of scope because it is an instance variable, but main is a static method. prus is out of scope because it is local to bilOng.

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

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