Iterators

 

ArrayList a = new ArrayList();
    a.add("joe");
   a.add("pete");
   a.add("sue");
   a.add("mary");
   Iterator i = a.iterator();
   while (i.hasNext())
     {System.out.println(i.next().;  // next returns Object and moves to next element
     }
_____________________________________________________________
ArrayList a = new ArrayList();
    a.add("joe");
   a.add("pete");
   a.add("sue");
   a.add("mary");
   Iterator i = a.iterator();
   while (i.hasNext())
     {System.out.println(i.next().length());    // wonít work Ė Objects donít have lengths
     }
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ArrayList a = new ArrayList();
    a.add("joe");
   a.add("pete");
   a.add("sue");
   a.add("mary");
   Iterator i = a.iterator();    // declare type of Iterator
   while (i.hasNext())
     {System.out.println(i.next().length());     // this does work
     }
_____________________________________________
ArrayList a = new ArrayList();
    a.add("joe");
   a.add("pete");
   a.add("sue");
   a.add("mary");
   Iterator i = a.iterator();
   while (i.hasNext())
     {if (i.next().equals("sue"))
       i.remove();                  // use of remove in iterator
         }
for (String s : a)               // new for loop - sue is gone
   {System.out.println(s);
    }

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For LinkedList deleteOdd1 is more efficient because we don't have to traverse
list to find #. For ArrayList - either is equally efficient.

import java.io.*;
import java.util.*;

public class Adder
 {private ArrayList list = new ArrayList();
    or
  private LinkedList list = new LinkedList();

     
    input in = new input();
    
  public  void enter()
       {for (int x=1; x <= 5; x++)
           {list.add((int)(Math.random()*100));   // note we didn't need to convert
            }
    }

            
      public void deleteOdd1()
        {Iterator a = list.iterator();
             while (a.hasNext())
              {if (a.next() % 2 == 1)
                a.remove();
            }
            }
            
          public void deleteOdd2()
            {int x = 0;
             while (x < list.size(); x++)
                 {
                   if (list.get(x) %2 ==1)
                    list.remove(x);
                   else
                      x++;
                }      
}
}