Variable scope and lifetime: Correct Solution

Given the following code:

public class Malbas {
    private int iana = 0;

    public void gass(int onod) {
        int flen = 0;
        A
        vu += onod;
        flen += onod;
        iana += onod;
        System.out.println("vu=" + vu + "  flen=" + flen + "  iana=" + iana);
    }

    public static void main(String[] args) {
        B
        Malbas m0 = new Malbas();
        Malbas m1 = new Malbas();
        m0.gass(1);
        m1 = new Malbas();
        m1.gass(10);
        m0 = m1;
        m0.gass(100);
        m1.gass(1000);
        C
    }

    private static int vu = 0;
}
  1. What does the main method print?
  2. Which of the variables [iana, vu, flen, m0, m1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    iana=1  vu=1  flen=1
iana=11  vu=10  flen=10
iana=111  vu=100  flen=110
iana=1111  vu=1000  flen=1110

  2. In scope at A : iana, flen, vu

  3. In scope at B : iana, m0

  4. In scope at C : iana

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

  1. iana is a static variable, flen is an instance variable, and vu is a local variable.

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

  3. At B , m1 is out of scope because it is not declared yet. flen is out of scope because it is an instance variable, but main is a static method. vu is out of scope because it is local to gass.

  4. At C , m0 and m1 are out of scope because they are not declared yet. flen is out of scope because it is an instance variable, but main is a static method. vu is out of scope because it is local to gass.

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