Answers to PAC Midterm Pt 1 from 2013

PracticeMidterm.java

// Question 1
public static boolean isVowell(char letter) {
    switch (letter) {
        case 'a':
        case 'e':
        case 'i':
        case 'o':
        case 'u':
            return true;
        case 'y':
            return Math.random() >= .5;
        default:
            return false;
    }
}

// Question 2
public static int[] append(int[] a, int[] b) {
    int[] c = new int[a.length + b.length];
    int i;
    for (i = 0; i < a.length; ++i) {
        c[i] = a[i];
    }
    for (; i < c.length; ++i) {
        c[i] = b[i - a.length];
    }
    return c;
}

what does

for (; i < c.length; ++i) {
        c[i] = b[i - a.length];
    }

means?

Hi Karen, in a 'for' loop you can optionally omit any of the components of the loop declaration.

In fact, this is legal..

for(;;) {
  // this is an infinite loop
}

Which may seem confusing at first, but is logically identical to..

while(true) {
  // also an infinite loop
}

In this case, I am not including the declaration of the counter 'for' the loop. The reason is that I already have a counter 'i' that contains the right starting value for the loop.

I could have done the following instead...

for (int j = i; j < c.length; ++j) {
    c[j] = b[j - a.length];
}

make sense?