Variable scope and lifetime: Correct Solution

Given the following code:

public class CelChelmer {
    public void gaegal(int me) {
        int tre = 0;
        A
        a += me;
        tre += me;
        iupa += me;
        System.out.println("a=" + a + "  tre=" + tre + "  iupa=" + iupa);
    }

    private int iupa = 0;

    public static void main(String[] args) {
        CelChelmer c0 = new CelChelmer();
        B
        CelChelmer c1 = new CelChelmer();
        C
        c0.gaegal(1);
        c1.gaegal(10);
        c1 = new CelChelmer();
        c0 = c1;
        c0.gaegal(100);
        c1.gaegal(1000);
    }

    private static int a = 0;
}
  1. What does the main method print?
  2. Which of the variables [iupa, a, tre, c0, c1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    iupa=1  a=1  tre=1
iupa=11  a=10  tre=10
iupa=111  a=100  tre=100
iupa=1111  a=1000  tre=1100

  2. In scope at A : iupa, tre, a

  3. In scope at B : iupa, c0, c1

  4. In scope at C : iupa, c0, c1

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

  1. iupa is a static variable, tre is an instance variable, and a is a local variable.

  2. At A , c0 and c1 out of scope because they are local to the main method.

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

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

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