Two Dimensional Arrays

This chapter expands our discussion on one-dimensional arrays to two dimensional arrays. A two dimensional array is a data structure that contains a collection of cells laid out in a two dimensional grid, similar to a table with rows and columns although the values are still stored linearly in memory. Each cell in a two dimensional array can be accessed through two indexes that specify the row number and column number respectively. Like s one dimensional array, the range of each index is from zero to the size of the row or column minus one. A nested for loop is commonly used to initialize, manipulate, and access the values in a two dimensional array.

14. Printing a 2D Array

Answer:How many rows must be printed?3
How many cells in each row must be printed?3 for row 0
2 for row 1
5 for row 3

Printing a 2D Array

Here is a program that creates a 2D array, then prints it out.

The nested loops are written to print out the correct number of cells for each row. The expression uneven[row].length evaluates to a different integer for each row of the array.



class unevenExample3
{
  public static void main( String[] arg )
  {
    // declare and construct a 2D array
    int[][] uneven = 
        { { 1, 9, 4 },
          { 0, 2},
          { 0, 1, 2, 3, 4 } };

    // print out the array
    for ( int row=0; row < uneven.length; row++ )
    {
      System.out.print("Row " + row + ": ");
      for ( int col=0; col < uneven[row].length; col++ )
        System.out.print( uneven[row][col] + " ");
      System.out.println();
    }

  }
}

Question 14:
For the print method to work, must every row of uneven be non-null?