15-100 Sections U-V-AA / Spring 2009 / Quiz 1
20 Minutes

SHOW YOUR WORK!

1. Arithmetic (Hundreds Digit)
Assuming the variable x holds a non-negative integer value, write one line of code that declares and initializes the integer y to hold the hundreds digit of x. For example, if x is 1234567, then y should be set to 5. If x is less than 100, then y should be set to 0.

2. Tracing
Indicate what the following will print. Show your work.

public static void main(String[] args) {
int x = 10, y = 3;
System.out.println(4 + x % y);
System.out.println(99 / x);
System.out.println(x / 99);
System.out.println(99 % x);
System.out.println(x % 99);
System.out.println(7 % 7 / 6 % 6);
}

3. Graphics + Arithmetic
For this part, assume a rectangle was drawn with the following method call (where a, b, c, and d all hold integer values between 100 and 200):
page.fillRect(a, b, c, d);
Now write a few lines of code that draws each of the following:

a. An oval centered inside the rectangle, with 20 pixels margin between each side of the oval and the corresponding side of the rectangle.

b. A second rectangle that is the mirror image of the first rectangle – of the same width and height, with the same top, but with its right edge as far from the right edge of the window as the first rectangle’s left edge is from the left edge of the window. You may not assume that “width” and “height” are set for you.

4. More Graphics + Arithmetic
In hw1, you were required to deal with the “thin white stripe” problem.

a. Very briefly explain the cause of the problem.

b. Very briefly describe one way to resolve the problem.

5. Bonus/Optional: Non-Zero Digits (Arithmetic)
Assuming the variable x holds a non-negative integer value less than one million, write a code snippet that declares and initializes the integer y to hold the number of non-zero digits in x. So, for example, if x is 102204, then y should be set to 4. Hint: you may want to write a helper method that takes a digit (or perhaps the Unicode value of a digit) and returns 0 if that digit is 0 and 1 otherwise (if it is 1 through 9).