Variable scope and lifetime: Correct Solution

Given the following code:

public class HulMehu {
    private static int tud = 0;
    private int up = 0;

    public void scang(int ie) {
        int eaer = 0;
        tud += ie;
        up += ie;
        eaer += ie;
        System.out.println("tud=" + tud + "  up=" + up + "  eaer=" + eaer);
        A
    }

    public static void main(String[] args) {
        HulMehu h0 = new HulMehu();
        B
        HulMehu h1 = new HulMehu();
        C
        h0.scang(1);
        h1 = h0;
        h0 = new HulMehu();
        h1.scang(10);
        h0.scang(100);
        h1.scang(1000);
    }
}
  1. What does the main method print?
  2. Which of the variables [eaer, tud, up, h0, h1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    eaer=1  tud=1  up=1
eaer=11  tud=11  up=10
eaer=111  tud=100  up=100
eaer=1111  tud=1011  up=1000

  2. In scope at A : eaer, tud

  3. In scope at B : eaer, h0, h1

  4. In scope at C : eaer, h0, h1

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

  1. eaer is a static variable, tud is an instance variable, and up is a local variable.

  2. At A , up is out of scope because it is not declared yet. h0 and h1 out of scope because they are local to the main method.

  3. At B , tud is out of scope because it is an instance variable, but main is a static method. up is out of scope because it is local to scang.

  4. At C , tud is out of scope because it is an instance variable, but main is a static method. up is out of scope because it is local to scang.

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