Variable scope and lifetime: Correct Solution

Given the following code:

public class Cusnin {
    private int he = 0;

    public static void main(String[] args) {
        A
        Cusnin c0 = new Cusnin();
        Cusnin c1 = new Cusnin();
        c0.longme(1);
        c1 = new Cusnin();
        c1.longme(10);
        c0 = c1;
        c0.longme(100);
        c1.longme(1000);
        B
    }

    public void longme(int spid) {
        int io = 0;
        C
        io += spid;
        e += spid;
        he += spid;
        System.out.println("io=" + io + "  e=" + e + "  he=" + he);
    }

    private static int e = 0;
}
  1. What does the main method print?
  2. Which of the variables [he, io, e, c0, c1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    he=1  io=1  e=1
he=10  io=11  e=10
he=100  io=111  e=110
he=1000  io=1111  e=1110

  2. In scope at A : io, c0

  3. In scope at B : io

  4. In scope at C : io, e, he

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

  1. io is a static variable, e is an instance variable, and he is a local variable.

  2. At A , c1 is out of scope because it is not declared yet. e is out of scope because it is an instance variable, but main is a static method. he is out of scope because it is local to longme.

  3. At B , c0 and c1 are out of scope because they are not declared yet. e is out of scope because it is an instance variable, but main is a static method. he is out of scope because it is local to longme.

  4. At C , c0 and c1 out of scope because they are local to the main method.

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