2D Arrays

Additional programming style guidelines:

/* 
 * 1. Make sure your program has indentation when is needed.
 * 2. Please include a comment line about local variables and group them all 
 *    together at the top of the program as long as it is not an OOD program.
 * 3. Never create a new local variable inside a loop!
 * 4. Have a blank line between different parts of the program
 */

final int COUNTRIES = 7;
final int MEDALS = 3;
int[][] counts = new int[COUNTRIES][MEDALS];

or but not both:

int[][] counts = {
 { 1, 0, 1 }, 
 { 1, 1, 0 }, 
 { 0, 0, 1 }, 
 { 1, 0, 0 }, 
 { 0, 1, 1 }, 
 { 0, 1, 1 }, 
 { 1, 1, 0 }
 };

for (int i = 0; i < COUNTRIES; i++)
{
  // Process the ith row
  for (int j = 0; j < MEDALS; j++) 
  {
      // Process the jth column in the ith row
      System.out.printf("%8d", counts[i][j]); 
  }
  System.out.println(); // Start a new line at the end of the row 
 }

for (int i = 0; i < counts.length; i++) 
{
  for (int j = 0; j < counts[0].length; j++) 
  {
     System.out.printf("%8d", counts[i][j]); 
  }
  System.out.println(); 
}

Accessing the neighboring elements of a 2D array

Adding by rows:

int total = 0;
for (int i = 0; i < COUNTRIES; i++)
{
  total = 0;
  for (int j = 0; j < MEDALS; j++) 
  {
    total = total + counts[i][j];
  }
}

Adding by columns:

int total = 0;
for (int j = 0; j < MEDALS; j++)
{
  total = 0;
  for (int i = 0; i < COUNTRIES; i++) 
  {
    total = total + counts[i][j]; 
  }
}

Classwork:
Write a program, MedalsTable_YI.java to produce the following output:

Assignment:
Consider as an example an 8 × 8 array for a board game:
int[][] board = new int[8][8];

BoardGame_YI.java: Using two nested loops, initialize the board using "for" loops so that zeroes and ones alternate, as on a checkerboard. Prompt the user for the size of the "square" 2D array and display the board on the screen.

0 1 0 1 0 1 0 1
1 0 1 0 1 0 1 0
0 1 0 1 0 1 0 1
...
1 0 1 0 1 0 1 0

Hint: Check whether i + j is even.