Variable scope and lifetime: Correct Solution

Given the following code:

public class Onled {
    public void pribme(int dida) {
        A
        int uss = 0;
        uss += dida;
        u += dida;
        as += dida;
        System.out.println("uss=" + uss + "  u=" + u + "  as=" + as);
    }

    private int u = 0;
    private static int as = 0;

    public static void main(String[] args) {
        B
        Onled o0 = new Onled();
        Onled o1 = new Onled();
        C
        o0.pribme(1);
        o1.pribme(10);
        o0 = o1;
        o1 = new Onled();
        o0.pribme(100);
        o1.pribme(1000);
    }
}
  1. What does the main method print?
  2. Which of the variables [as, uss, u, o0, o1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    as=1  uss=1  u=1
as=10  uss=10  u=11
as=100  uss=110  u=111
as=1000  uss=1000  u=1111

  2. In scope at A : u, uss, as

  3. In scope at B : u, o0

  4. In scope at C : u, o0, o1

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

  1. u is a static variable, uss is an instance variable, and as is a local variable.

  2. At A , o0 and o1 out of scope because they are local to the main method.

  3. At B , o1 is out of scope because it is not declared yet. uss is out of scope because it is an instance variable, but main is a static method. as is out of scope because it is local to pribme.

  4. At C , uss is out of scope because it is an instance variable, but main is a static method. as is out of scope because it is local to pribme.

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