Programming the design pattern

The first part of our source code includes import statements for ArrayList and Iterator. In the main() method, we create a colonies ArrayList of strings. We then populate 12 elements to the ArrayList:

import java.util.ArrayList;
import java.util.Iterator;

public class IteratorExample {

    public static void main(String[] args) {

        ArrayList<String> colonies = new ArrayList<>();

        colonies.add("Aerlion");
        colonies.add("Aquaria");
        colonies.add("Canceron");
        colonies.add("Caprica");
        colonies.add("Gemenon");
        colonies.add("Leonis");
        colonies.add("Libran");
        colonies.add("Picon");
        colonies.add("Sagittaron");
        colonies.add("Scorpia");
        colonies.add("Tauron");
        colonies.add("Virgon");

The second half of the source code does three things. First, it instantiates an iterator named myIterator. Next, a simple text header is printed to the console. Lastly, the code iterates through the ArrayList, printing each element:

        // instantiate iterator
        Iterator myIterator = colonies.iterator();

        // console output
        System.out.println("\n\nOriginal Colonies of Kobol:");

        // iterate through the list
        while (myIterator.hasNext())
        System.out.println("\t\t" + myIterator.next());

    }
}

The iteration was able to take place without knowing that the colonies object stored its data in an ArrayList.

The output of our sample application is illustrated here:

This section featured the source code and output, demonstrating the iterator design pattern.