ITERATOR PATTERN
                     BEHAVIORAL PATTERN
ITERATOR PATTERN
• Iterator Pattern is a relatively simple and frequently used design 
pattern. There are a lot of data structures/collections available in 
every language. Each collection must provide an iterator that lets it 
iterate through its objects. However while doing so it should make 
sure that it does not expose its implementation.
• Iterator pattern is very commonly used design pattern in Java and 
.Net programming environment. This pattern is used to get a way to 
access the elements of a collection object in sequential manner 
without any need to know its underlying representation. 
Implementation
create a Iterator interface which narrates navigation method and 
a Containerinterface which retruns the iterator 
Concrete classes implementing the Container interface will be 
responsible to implement Iterator interface and use it
IteratorPatternDemo, our demo class will use NamesRepository, a 
concrete class implementation to print a Names stored as a collection 
in NamesRepository.
UML DIAGRAM
Step 1
Create interfaces
• Iterator.java
public interface Iterator 
{
 public boolean hasNext(); 
public Object next(); 
}
Container.java
public interface Container 
{ 
public Iterator getIterator();
 }
Step 2
Create concrete class implementing 
the Container interface. This class has inner 
class NameIterator implementing 
•thNaem eItReeproasittooryr.j aivnaterface.
public class NameRepository implements Container 
{
 public String names[] = {"Robert" , "John" ,"Julie" , "Lora"};
 @
Override 
public Iterator getIterator() 
{ 
return new NameIterator();
 }
private class NameIterator implements Iterator
 {
 int index; 
@Override 
public boolean hasNext() 
{ 
if(index < names.length)
{ 
return true; 
} 
return false;
 }
@Override 
Public Object next() 
{
   if(this.hasNext()
{ 
     return names[index++];
 } 
 return null; 
}
}
}
Step 3
 Use the NameRepository to get iterator and 
print names.
• IteratorPatternDemo.java
public class IteratorPatternDemo 
{
 public static void main(String[] args) 
  {
     NameRepository namesRepository = new NameRepository();
for(Iterator iter = 
namesRepository.getIterator();iter.hasNext();)
     { 
        String name = (String)iter.next(); 
        System.out.println("Name : " + name); 
      } 
  } 
}
Step 4
 Verify the output.
Name : Robert 
 Name : John 
Name : Julie 
Name : Lora