Implementation of Iterator methods

Question

I am working with collections. One thing which is bothering me is: where is the Implementations of the methods of java.util.Iterator Interface? In which class these methods are implemented?

 public abstract boolean hasNext();
 public abstract E next();
 public abstract void remove();

I searched the source code of the java API, but didn't find the implementation of these methods in any class.

For example: grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/… — assylias
– assylias, Commented Sep 2, 2012 at 7:00
@jayan:i searched in a java.lang.util package the implementation classes — kTiwari
– kTiwari, Commented Sep 2, 2012 at 7:03

Gopal · Accepted Answer · 2012-09-02 06:58:02Z

7

Iterator is an interface and it has around 50 implementations in the java api itself. Since the iterator needs to compy with the iterating object type, for ex if you want to iterate an ArrayList the iterator instance which your iterator() method returns is of new Itr type. see the implementation in java.util.AbstractList class which forms the base class for ArrayList

answered Sep 2, 2012 at 6:58

Gopal

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Comments

Subhrajyoti Majumder · Accepted Answer · 2012-09-02 07:37:58Z

1

There are multiple classes in JDK where It has been implemented. ArrayList is very good example for your concern. You can go through the code in openJDK. And the iterator method defination is -

  public Iterator<E> iterator() {
         return new Itr();
     }

Where This Itr private class implements Iterator<E> and define all itarator method.

edited Sep 2, 2012 at 7:37

answered Sep 2, 2012 at 7:17

Subhrajyoti Majumder

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Comments

zhaoyw · Accepted Answer · 2012-09-02 07:02:06Z

0

You can search java apis who implements Iterator. Those classes all have implements the above methods. Go to browse the jdk source code. It will help you a lot.

answered Sep 2, 2012 at 7:02

zhaoyw

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2 Comments

zhaoyw Over a year ago

AbstractList has what you want. you can try.

zhaoyw Over a year ago

it has two inner class describe the iterator.

Bharat Sinha · Accepted Answer · 2012-09-02 07:06:36Z

0

In case you are using eclipse and you have source code configured in eclipse itself.

Just select the method and press Ctrl + T (show type hierarchy) and you can see all the classes in which the method has been implemented.

answered Sep 2, 2012 at 7:06

Bharat Sinha

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