/** March.java - Let's simulate a group of people "marching" around a field.
 *  We'll display a 2-d array, and then tell our people to move 1 square
 *  in various directions.  Purpose is to practice with 2-d arrays.
 *  Since I'm going to use i and j a lot in this program, I'll just declare
 *  them once at the top.
 */
public class March
{
  public static void main(String [] args)
  {
    int [][] a = new int[10][10];
    int i, j;

    // Initialize.  Use 0 to represent an empty cell.
    for (i = 0; i < a.length; ++i)
      for (j = 0; j < a[0].length; ++j)
        if (i >= 2 && i <= 6 && j >= 2 && j <= 6)
          a[i][j] = 1;
        else
          a[i][j] = 0;

    // Display
    for (i = 0; i < a.length; ++i)
    {
      for (j = 0; j < a[0].length; ++j)
        System.out.print("" + a[i][j] + " ");
      System.out.println();
    }
    System.out.println();

    // Move right!  Do the same thing for every row.
    for (i = 0; i < a.length; ++i)
    {
      for (j = 2; j <= 6; ++j)
      {
        a[i][j+1] = a[i][j];
      }
      a[i][2] = 0;
    }

    // Display again
    System.out.println("After moving to the right:");
    for (i = 0; i < a.length; ++i)
    {
      for (j = 0; j < a[0].length; ++j)
        System.out.print("" + a[i][j] + " ");
      System.out.println();
    }
    System.out.println();

    // Can we move up?  I'm assuming that the data is in rows 2-6
    // and columns 3-7 before the move.
    for (j = 3; j <= 7; ++j)
    {
      for (i = 2; i <=6; ++i)
        a[i-1][j] = a[i][j];
      a[6][j] = 0;
    }
  
    // Display again
    System.out.println("After moving UP:");
    for (i = 0; i < a.length; ++i)
    {
      for (j = 0; j < a[0].length; ++j)
        System.out.print("" + a[i][j] + " ");
      System.out.println();
    }
    System.out.println();
  }
}