If we have an array of number in no particular order, we might want to sort them into ascending or descending order. This is called sorting. The most basic sorting algorithm is called Bubble Sort. Here it is:

public class sorting
{
 public static void main( String args[] )
 {
   int my_array[] = { 2, 6, 4, 8, 10, 12, 89, 68, 45, 37 };
   boolean there_was_a_swap = false;

   showArray( my_array );
   for ( int c=0; c < my_array.length ; c++ )
      {
      for ( int element = 0 ; element < my_array.length-1 ; element++ )
         {
         if ( my_array[element] > my_array[element + 1] )
             {  
             swap( my_array, element, element + 1 );
             there_was_a_swap = true;
             }
         }//end inner for loop

      if ( there_was_a_swap == false )
          {
          break;
          }
      }//end outer for loop, end sorting algorithm
   showArray( my_array );
     }//end main
 public static void showArray( int array[] )
 {
  for ( int c = 0 ; c < array.length ; c++ )
  {
   System.out.print( array[c]+", " );
  }
  System.out.println( );
  return;
 }
 
 public static void swap( int sorting_array[], int i, int j )
 {
  int hold = sorting_array[i];
  sorting_array[i] = sorting_array[j];
  sorting_array[j] = hold;
  return;
 }
}//end class

This is called bubble sort because the correct values bubble up to the surface. We must traverse n numbers n times, or n^2 times. We could improve the efficiency a bit by noticing that we do not need to check the last element which was put into its correct place. Try to improve the above program in this way.

© Nachum Danzig December 2003