Variable scope and lifetime: Correct Solution

Given the following code:

public class Kesfeng {
    private static int he = 0;
    private int upri = 0;

    public void sirru(int pi) {
        int bata = 0;
        A
        he += pi;
        bata += pi;
        upri += pi;
        System.out.println("he=" + he + "  bata=" + bata + "  upri=" + upri);
    }

    public static void main(String[] args) {
        B
        Kesfeng k0 = new Kesfeng();
        Kesfeng k1 = new Kesfeng();
        k0.sirru(1);
        k1 = new Kesfeng();
        k1.sirru(10);
        k0 = k1;
        k0.sirru(100);
        k1.sirru(1000);
        C
    }
}
  1. What does the main method print?
  2. Which of the variables [upri, he, bata, k0, k1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    upri=1  he=1  bata=1
upri=11  he=10  bata=10
upri=111  he=100  bata=110
upri=1111  he=1000  bata=1110

  2. In scope at A : upri, bata, he

  3. In scope at B : upri, k0

  4. In scope at C : upri

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

  1. upri is a static variable, bata is an instance variable, and he is a local variable.

  2. At A , k0 and k1 out of scope because they are local to the main method.

  3. At B , k1 is out of scope because it is not declared yet. bata 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 sirru.

  4. At C , k0 and k1 are out of scope because they are not declared yet. bata 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 sirru.

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