Variable scope and lifetime: Correct Solution

Given the following code:

public class Itrul {
    private int ridi = 0;
    private static int he = 0;

    public void crosta(int rau) {
        int ent = 0;
        he += rau;
        ent += rau;
        ridi += rau;
        System.out.println("he=" + he + "  ent=" + ent + "  ridi=" + ridi);
        A
    }

    public static void main(String[] args) {
        Itrul i0 = new Itrul();
        B
        Itrul i1 = new Itrul();
        i0.crosta(1);
        i1.crosta(10);
        i0.crosta(100);
        i1 = i0;
        i0 = new Itrul();
        i1.crosta(1000);
        C
    }
}
  1. What does the main method print?
  2. Which of the variables [ridi, he, ent, i0, i1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ridi=1  he=1  ent=1
ridi=11  he=10  ent=10
ridi=111  he=100  ent=101
ridi=1111  he=1000  ent=1101

  2. In scope at A : ridi, ent

  3. In scope at B : ridi, i0, i1

  4. In scope at C : ridi

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

  1. ridi is a static variable, ent is an instance variable, and he is a local variable.

  2. At A , he is out of scope because it is not declared yet. i0 and i1 out of scope because they are local to the main method.

  3. At B , ent 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 crosta.

  4. At C , i0 and i1 are out of scope because they are not declared yet. ent 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 crosta.

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