Variable scope and lifetime: Correct Solution

Given the following code:

public class Slai {
    public void evueng(int so) {
        int sior = 0;
        A
        mur += so;
        apor += so;
        sior += so;
        System.out.println("mur=" + mur + "  apor=" + apor + "  sior=" + sior);
    }

    private int mur = 0;

    public static void main(String[] args) {
        B
        Slai s0 = new Slai();
        Slai s1 = new Slai();
        s0.evueng(1);
        s1.evueng(10);
        s0 = s1;
        s0.evueng(100);
        s1 = new Slai();
        s1.evueng(1000);
        C
    }

    private static int apor = 0;
}
  1. What does the main method print?
  2. Which of the variables [sior, mur, apor, s0, s1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    sior=1  mur=1  apor=1
sior=10  mur=11  apor=10
sior=110  mur=111  apor=100
sior=1000  mur=1111  apor=1000

  2. In scope at A : mur, sior, apor

  3. In scope at B : mur, s0

  4. In scope at C : mur

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

  1. mur is a static variable, sior is an instance variable, and apor is a local variable.

  2. At A , s0 and s1 out of scope because they are local to the main method.

  3. At B , s1 is out of scope because it is not declared yet. sior is out of scope because it is an instance variable, but main is a static method. apor is out of scope because it is local to evueng.

  4. At C , s0 and s1 are out of scope because they are not declared yet. sior is out of scope because it is an instance variable, but main is a static method. apor is out of scope because it is local to evueng.

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