ArrayLists and Iterators

18. Enhanced for Loop

Answer:
Iterator <Integer> visitor = primes.iterator() ;

`Enhanced for Loop`

The enhanced for loop (sometimes called a "for each" loop) can be used with any class that implements the Iterable interface, such as ArrayList. Here is the previous program, now written using an enhanced for loop.


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

    names.add( "Amy" );    names.add( "Bob" ); 
    names.add( "Chris" );  names.add( "Deb" ); 
    names.add( "Elaine" ); names.add( "Frank" );
    names.add( "Gail" );   names.add( "Hal" );
    
    for ( String nm : names ) 
      System.out.println( nm );
  }
}

The program does the same thing as the previous program. The enhanced for loop accesses the String references in names and assigns them one-by-one to nm. With an enhanced for loop there is no danger an index will go out of bounds. (There is a colon : separating nm and names in the above. This might be hard to see in your browser.)

The enhanced for loop only visits those cells that are not empty, beginning with cell zero. Since an ArrayList never has gaps between cells, all occupied cells are visited.

Question 18:

(Review: ) Can primitive types, like int and double be added to an ArrayList ?