Good programming practices: creating Iterator objects

Question

Hi,
This is a question about Good programming practices for creating Iterator objects of ArrayList objects. The following line of code works fine in my program (as ridiculous as it may sound):
        Iterator cheesesIterator = cheeses.iterator();but I was wondering whether Java is automatically inserting the <Type> and new code to make:
        Iterator<String> cheesesIterator = new cheeses.iterator();and therefore whether it is good practice to use these everytime? Thank you. ("full" code shown below:)
import java.util.ArrayList;
import java.util.Iterator;
public class DemonstrateIterator
    private ArrayList<String>  cheeses;
     * constructor:
    public DemonstrateIterator()
        cheeses = new ArrayList<String>();
        cheeses.add("Emmentaler");
        cheeses.add("Cheddar");
        cheeses.add("Stilton");
        cheeses.add("Brie");
        cheeses.add("Roquefort");
    public void listCheeses()
         //make an iterator object of the ArrayList object
        Iterator cheesesIterator = cheeses.iterator();
        while (cheesesIterator.hasNext()) {
            System.out.println(cheesesIterator.next());
        /** Exploring the toString and Super functions. **/       
        System.out.println("\na toString call to Super returns: " +
                                          super.toString() + "\n");
}

Answer 1

AJ-Phil wrote:
Hi,
This is a question about Good programming practices for creating Iterator objects of ArrayList objects. The following line of code works fine in my program (as ridiculous as it may sound):
        Iterator cheesesIterator = cheeses.iterator();but I was wondering whether Java is automatically inserting the <Type> and new code to make:
        Iterator<String> cheesesIterator = new cheeses.iterator();and therefore whether it is good practice to use these everytime? TFirst, new chesses.iterator() won't compile.
iterator() is just a method that returns an iterator. It constructs an instance of a private or nested class that implements iterator, and returns a reference to it.
As for the <T>, when you declare List<String>, that parameterizes that list with type String. The iterator() method returns Iterator<T>. You can look at the source code for yourself. It's in src.zip that came with your JDK download.
Separate from that is your declaration of that variable as type Iterator, rather than Iterator<String>. Regardless of what you declare on the LHS, the iterator() method returns Iterator<T>. Your bare Iterator is essentially Iterator<Object> or Iterator<? extends Object> (not sure which, or what the difference is), which is assignment compatible with Iterator<T>. If you had declared it Iterator<String>, you wouldn't have to cast after calling next().
Edited by: jverd on Nov 23, 2008 11:33 AM