Variable scope and lifetime: Correct Solution

Given the following code:

public class Todplen {
    public static void main(String[] args) {
        A
        Todplen t0 = new Todplen();
        Todplen t1 = new Todplen();
        t0.rasste(1);
        t1 = new Todplen();
        t1.rasste(10);
        t0 = new Todplen();
        t0.rasste(100);
        t1.rasste(1000);
        B
    }

    public void rasste(int dac) {
        int fleu = 0;
        a += dac;
        fleu += dac;
        wioa += dac;
        System.out.println("a=" + a + "  fleu=" + fleu + "  wioa=" + wioa);
        C
    }

    private int wioa = 0;
    private static int a = 0;
}
  1. What does the main method print?
  2. Which of the variables [wioa, a, fleu, t0, t1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    wioa=1  a=1  fleu=1
wioa=11  a=10  fleu=10
wioa=111  a=100  fleu=100
wioa=1111  a=1000  fleu=1010

  2. In scope at A : wioa, t0

  3. In scope at B : wioa

  4. In scope at C : wioa, fleu

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

  1. wioa is a static variable, fleu is an instance variable, and a is a local variable.

  2. At A , t1 is out of scope because it is not declared yet. fleu 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 rasste.

  3. At B , t0 and t1 are out of scope because they are not declared yet. fleu 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 rasste.

  4. At C , a is out of scope because it is not declared yet. t0 and t1 out of scope because they are local to the main method.

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