Computer Science 2

Generic Methods Exercises

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Vector

1. Discuss with someone else the difference between ArrayList and Vector classes
2. Declare a Vector object that stores the vowels in the English alphabet ('a', 'e', 'i', 'o', 'u' and 'y'). Display each of it's elements on a separate line.

Generic Methods

1. Discuss with someone else an advantage of using generics
2. Convert the following method to be a generic method:

   /**
    * Swap the elements at two indices
    * <p>Note: Does not check if the indices are valid</p>
    * @param array The array
    * @param index1 The index of one of the elements to swap
    * @param index2 The index of other element to swap
    */
   public static void swap2( Integer[] array, int index1, int index2 ){
       Integer temp = array[index1];
       array[ index1 ] = array[ index2 ];
       array[ index2 ] = temp;
   }
   
   public static void main( String[] args ){
       Integer[] nums = {1,2,3};
       Character[] hello = {'h', 'e', 'l', 'l', 'o'};
   
       for( int i : nums ){
           System.out.print( i );
       }
   
       swap2( nums, 1, 2 );
       for( int i : nums ){
           System.out.print( i );
       }
       System.out.println("\n");
   
       for( Character c : hello ){
           System.out.print( c );
       }
   
       swap2( hello, 1, 2 );
       for( Character c : hello ){
           System.out.print( c );
       }
       System.out.println("\n");
   }

3. Does the following method compile? If not, why? source

   import java.util.List;
   
   /**	    
    * Display all of the numbers (whole or real) in a list on one line
    * @param lst A list of Numbers
    */
   public <T extends Number> void printList(List<T> lst) {
       for( Number n : lst )
           System.out.print(n + " ");
       System.out.println();
   }

4. Write a generic method to match the following Javadoc. Additionally, add code to main() to call the method twice (each with a different type).

   /**
    * Finds the minimum value in a list between two indices
    * <p>Note: Does not check if the indices are valid</p>
    * @param lst The list object
    * @param startIndex The index to start looking at
    * @param endIndex The last index to consider
    * @return The smallest value in lst between startIndex and endIndex (inclusive) 
    */

   Note, "<" and ">" can only be used for primitives. However, any object that implements the Comparable< T > interface can call compareTo( T otherObj ).