Variable scope and lifetime: Correct Solution

Given the following code:

public class Muaac {
    private static int ded = 0;
    private int bi = 0;

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

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

Solution

  1. Output:

    bi=1  ne=1  ded=1
bi=10  ne=11  ded=10
bi=100  ne=111  ded=101
bi=1000  ne=1111  ded=1101

  2. In scope at A : ne, m0, m1

  3. In scope at B : ne

  4. In scope at C : ne, ded, bi

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

  1. ne is a static variable, ded is an instance variable, and bi is a local variable.

  2. At A , ded is out of scope because it is an instance variable, but main is a static method. bi is out of scope because it is local to porass.

  3. At B , m0 and m1 are out of scope because they are not declared yet. ded is out of scope because it is an instance variable, but main is a static method. bi is out of scope because it is local to porass.

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

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