Variable scope and lifetime: Correct Solution

Given the following code:

public class Gism {
    public static void main(String[] args) {
        A
        Gism g0 = new Gism();
        Gism g1 = new Gism();
        B
        g0.rene(1);
        g1.rene(10);
        g0 = new Gism();
        g0.rene(100);
        g1 = g0;
        g1.rene(1000);
    }

    private int cel = 0;
    private static int slac = 0;

    public void rene(int as) {
        C
        int vec = 0;
        vec += as;
        cel += as;
        slac += as;
        System.out.println("vec=" + vec + "  cel=" + cel + "  slac=" + slac);
    }
}
  1. What does the main method print?
  2. Which of the variables [slac, vec, cel, g0, g1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    slac=1  vec=1  cel=1
slac=10  vec=10  cel=11
slac=100  vec=100  cel=111
slac=1000  vec=1100  cel=1111

  2. In scope at A : cel, g0

  3. In scope at B : cel, g0, g1

  4. In scope at C : cel, vec, slac

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

  1. cel is a static variable, vec is an instance variable, and slac is a local variable.

  2. At A , g1 is out of scope because it is not declared yet. vec is out of scope because it is an instance variable, but main is a static method. slac is out of scope because it is local to rene.

  3. At B , vec is out of scope because it is an instance variable, but main is a static method. slac is out of scope because it is local to rene.

  4. At C , g0 and g1 out of scope because they are local to the main method.

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