Question

If you call this first method, ‘CreateLotsOfAlphas’, what is it supposed to print? I’m just having trouble following the flow of the program. I thought it would print aabbc, but for some reason it actually prints bacbc.

My reasoning is that newA1.y is just the input, a, at first due to the null. a is saved into this.y, so newA2.y is (a + b) with b saved into this.y, then newA3.y is (b + c) to give aabbc.

Am I looking at this wrong or something?

public void CreateLotsOfAlphas() {
    Alpha newA1 = new Alpha(1.0, "a", null); 
    Alpha newA2 = new Alpha(2.0, "b", newA1); 
    Alpha newA3 = new Alpha(3.0, "c", newA2);
    System.out.println(newA1.y + newA2.y + newA3.y);
}

These two methods are in two different classes by the way.

public Alpha(double x, String y, Alpha oldAlpha) { 
    this.x = x;
    this.y = y;
    w = (int) x;
    if (oldAlpha != null) { 
        oldAlpha.y = y + oldAlpha.y;
    } 
}

Answer 1

Alpha newA1 = new Alpha(1.0, "a", null);
// oldAlpha == null so we only newA1.y = "a"
Alpha newA2 = new Alpha(2.0, "b", newA1);
// oldAlpha is newA1 => newA1.y = "b"+"a"; newA2.y = "b"
Alpha newA3 = new Alpha(3.0, "c", newA2);
// oldAlpha is newA2 => newA2.y = "c"+"b", newA3.y = "c"; newA1.y = "ba" (still)
System.out.println(newA1.y + newA2.y + newA3.y);
// newA1.y = "ba", newA2.y = "cb", newA3.y = "c"

… clear enough?