Variable scope and lifetime: Correct Solution

Given the following code:

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

    public void putol(int ost) {
        C
        int risi = 0;
        risi += ost;
        so += ost;
        trif += ost;
        System.out.println("risi=" + risi + "  so=" + so + "  trif=" + trif);
    }

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

Solution

  1. Output:

    trif=1  risi=1  so=1
trif=10  risi=11  so=10
trif=100  risi=111  so=110
trif=1000  risi=1111  so=1000

  2. In scope at A : risi, t0

  3. In scope at B : risi

  4. In scope at C : risi, so, trif

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

  1. risi is a static variable, so is an instance variable, and trif is a local variable.

  2. At A , t1 is out of scope because it is not declared yet. so is out of scope because it is an instance variable, but main is a static method. trif is out of scope because it is local to putol.

  3. At B , t0 and t1 are out of scope because they are not declared yet. so is out of scope because it is an instance variable, but main is a static method. trif is out of scope because it is local to putol.

  4. At C , t0 and t1 out of scope because they are local to the main method.

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