Variable scope and lifetime: Correct Solution

Given the following code:

public class Hosber {
    public static void main(String[] args) {
        Hosber h0 = new Hosber();
        A
        Hosber h1 = new Hosber();
        B
        h0.rass(1);
        h1.rass(10);
        h0 = h1;
        h1 = new Hosber();
        h0.rass(100);
        h1.rass(1000);
    }

    public void rass(int ro) {
        int ra = 0;
        C
        ea += ro;
        scha += ro;
        ra += ro;
        System.out.println("ea=" + ea + "  scha=" + scha + "  ra=" + ra);
    }

    private static int ea = 0;
    private int scha = 0;
}
  1. What does the main method print?
  2. Which of the variables [ra, ea, scha, h0, h1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    ra=1  ea=1  scha=1
ra=11  ea=10  scha=10
ra=111  ea=110  scha=100
ra=1111  ea=1000  scha=1000

  2. In scope at A : ra, h0, h1

  3. In scope at B : ra, h0, h1

  4. In scope at C : ra, ea, scha

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

  1. ra is a static variable, ea is an instance variable, and scha is a local variable.

  2. At A , ea is out of scope because it is an instance variable, but main is a static method. scha is out of scope because it is local to rass.

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

  4. At C , h0 and h1 out of scope because they are local to the main method.

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