Variable scope and lifetime: Correct Solution

Given the following code:

public class Lumfas {
    public void erus(int hil) {
        int fres = 0;
        fres += hil;
        pid += hil;
        ces += hil;
        System.out.println("fres=" + fres + "  pid=" + pid + "  ces=" + ces);
        A
    }

    public static void main(String[] args) {
        Lumfas l0 = new Lumfas();
        B
        Lumfas l1 = new Lumfas();
        C
        l0.erus(1);
        l1.erus(10);
        l0.erus(100);
        l0 = new Lumfas();
        l1 = new Lumfas();
        l1.erus(1000);
    }

    private static int pid = 0;
    private int ces = 0;
}
  1. What does the main method print?
  2. Which of the variables [ces, fres, pid, l0, l1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ces=1  fres=1  pid=1
ces=10  fres=11  pid=10
ces=100  fres=111  pid=101
ces=1000  fres=1111  pid=1000

  2. In scope at A : fres, pid

  3. In scope at B : fres, l0, l1

  4. In scope at C : fres, l0, l1

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

  1. fres is a static variable, pid is an instance variable, and ces is a local variable.

  2. At A , ces is out of scope because it is not declared yet. l0 and l1 out of scope because they are local to the main method.

  3. At B , pid is out of scope because it is an instance variable, but main is a static method. ces is out of scope because it is local to erus.

  4. At C , pid is out of scope because it is an instance variable, but main is a static method. ces is out of scope because it is local to erus.

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