9.1.7 Checkerboard V2 | Answers

The fluorescent lights of the computer lab hummed, a soundtrack to the mounting panic of a dozen Intro to Java students. It was Friday, 3:45 PM. The deadline for the "Nested Loops" unit was looming like a storm cloud.

Common Errors and How to Fix Them

Even with the correct code, students often hit frustrating roadblocks. Here’s a quick troubleshooting table: 9.1.7 checkerboard v2 answers

Using nested loops (rows and columns)
Determining square color based on (row + column) % 2 == 0
Drawing with a graphics library or printing with characters (X and O, or # and )

Key Concepts You Must Understand

Nested Loops: An outer loop for rows, an inner loop for columns.
Modulus Operator (%): Used to decide the color. (row + column) % 2 == 0 is the classic checkerboard formula.
Coordinates: Each square’s (x, y) position is calculated by multiplying the loop counter by the square width/height.
GRect: The GRect class from the ACM graphics library is used to create rectangles.

# Usage board = Checkerboard() board.print_board()

| Error Message / Symptom | Likely Cause | Solution | |-------------------------|--------------|----------| | Square is not filled | Missing setFilled(true) | Add the line before setting the color. | | All squares are the same color | Incorrect modulus logic | Use (row + col) % 2 == 0. Check your starting color. | | ArrayIndexOutOfBoundsException | Using <= instead of < in loop | Ensure loops run 0 to 7 (not 0 to 8). | | Nothing appears on screen | Forgot to call add(square) | After creating and coloring, call add(square). | | Squares overlap or have gaps | Incorrect coordinate math | x = col * size, y = row * size. Don’t add extra offset. | | Autograder fails on style | Missing constants or comments | Use private static final int for magic numbers (8, 50). | The fluorescent lights of the computer lab hummed,