Variable scope and lifetime: Correct Solution

Given the following code:

public class Menkam {
    private static int ina = 0;

    public static void main(String[] args) {
        A
        Menkam m0 = new Menkam();
        Menkam m1 = new Menkam();
        B
        m0.sinmic(1);
        m1.sinmic(10);
        m0.sinmic(100);
        m1 = new Menkam();
        m0 = m1;
        m1.sinmic(1000);
    }

    private int spu = 0;

    public void sinmic(int ahed) {
        int er = 0;
        C
        spu += ahed;
        er += ahed;
        ina += ahed;
        System.out.println("spu=" + spu + "  er=" + er + "  ina=" + ina);
    }
}
  1. What does the main method print?
  2. Which of the variables [ina, spu, er, m0, m1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ina=1  spu=1  er=1
ina=10  spu=10  er=11
ina=101  spu=100  er=111
ina=1000  spu=1000  er=1111

  2. In scope at A : er, m0

  3. In scope at B : er, m0, m1

  4. In scope at C : er, ina, spu

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

  1. er is a static variable, ina is an instance variable, and spu is a local variable.

  2. At A , m1 is out of scope because it is not declared yet. ina is out of scope because it is an instance variable, but main is a static method. spu is out of scope because it is local to sinmic.

  3. At B , ina is out of scope because it is an instance variable, but main is a static method. spu is out of scope because it is local to sinmic.

  4. At C , m0 and m1 out of scope because they are local to the main method.

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