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.

15. Null Rows



Answer:
Yes. If a row does not exists (and therefore uneven[row] is null) the following code will throw an Exception:
for ( int col=0; col < uneven[row].length; col++ )






Null Rows



    

    

    
Here is a somewhat improved version of the program that tests each row to see if it exists. If the row exists, its length is used:

    

    

    

        
            

            

            

                
                    



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

                		
            

        
    

However, the code does assume that uneven is non-null.







    
Question 15:
(Thought Question: ) Are 3-dimensional arrays possible?