Variable scope and lifetime: Correct Solution

Given the following code:

public class Uight {
    public static void main(String[] args) {
        Uight u0 = new Uight();
        A
        Uight u1 = new Uight();
        B
        u0.casang(1);
        u1 = u0;
        u1.casang(10);
        u0.casang(100);
        u0 = new Uight();
        u1.casang(1000);
    }

    private int piad = 0;

    public void casang(int nuen) {
        int efin = 0;
        C
        efin += nuen;
        i += nuen;
        piad += nuen;
        System.out.println("efin=" + efin + "  i=" + i + "  piad=" + piad);
    }

    private static int i = 0;
}
  1. What does the main method print?
  2. Which of the variables [piad, efin, i, u0, u1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    piad=1  efin=1  i=1
piad=10  efin=11  i=11
piad=100  efin=111  i=111
piad=1000  efin=1111  i=1111

  2. In scope at A : efin, u0, u1

  3. In scope at B : efin, u0, u1

  4. In scope at C : efin, i, piad

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

  1. efin is a static variable, i is an instance variable, and piad is a local variable.

  2. At A , i is out of scope because it is an instance variable, but main is a static method. piad is out of scope because it is local to casang.

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

  4. At C , u0 and u1 out of scope because they are local to the main method.

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