ArrayLists and Iterators

Read this chapter about lists and the useful methods that are available for adding and inserting elements into a list. 

15. isEmpty()



Answer:
0: Amy
1: Bob
2: Deb



    

        
isEmpty()

        

    





    

        

        

        

    







    












To check if an ArrayList has elements use
boolean isEmpty()
which returns true if the cells of the ArrayList are all empty.
Warning:The value null in a cell counts as data. An empty cell is not the same as a cell that contains null.
To remove all elements from a list, use
void clear()





    
Question 15:
(Puzzle: ) What will the following program print?

    
        

        

        

                           
import java.util.* ;
public class NullPuzzle
{
  public static void main ( String[] args)
  {
    ArrayList<String> nobby = new ArrayList<String>();

    System.out.println( "Case A:" + nobby.isEmpty() );
    
    nobby.add( null );    
    System.out.println( "Case B:" + nobby.isEmpty() );
    
    nobby.remove( 0 );  
    System.out.println( "Case C:" + nobby.isEmpty() );
    
    nobby.add( "" );    
    System.out.println( "Case D:" + nobby.isEmpty() );
    
    nobby.clear( );    
    System.out.println( "Case E:" + nobby.isEmpty() );

  }
}