Using Iterators

Question

I have a very basic question in mind. An Iterator is an interface so to create an object we will need to create a class that implements Iterator and then create an object for the same. But when i saw the use of iterator it confused me as we are referencing an interface directly without having a class that implements it. for example :

HashMap map = new HashMap();
   map.put("1", "One");
   map.put("2", "Two");
   Iterator i = map.entrySet().iterator();

how come we have an object of an Interface!!

@AlexStybaev it will get you a new HashMap instance that can be accessed like any Map. — DerMike
– DerMike, Commented May 14, 2012 at 11:06
@DerMike i know it. That is just the same as for Iterator, isn't it? Just an implementation of Iterator interface. — Alex Stybaev
– Alex Stybaev, Commented May 14, 2012 at 11:09
I think the problem is that @Amit doesn't see class which implements Iterator returned by iterator method. This class is inner class in HashMap and is not public. Here it is. — Mikita Belahlazau
– Mikita Belahlazau, Commented May 14, 2012 at 11:11

stacker · Accepted Answer · 2012-05-14 11:04:18Z

5

Iterator is a interface, but map.entrySet().iterator() returns an object which implements the Iterator interface.

answered May 14, 2012 at 11:04

stacker

69.1k29 gold badges143 silver badges213 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Mikita Belahlazau Over a year ago

To add: here is real class which used by HashMap. grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/…

DerMike · Accepted Answer · 2012-05-14 11:04:05Z

0

You'll get some implementation from that call. You just cannot assume more than the things that are enforced (and documented) be the iterator interface. Look for "anonymous inner class".

answered May 14, 2012 at 11:04

DerMike

16.3k14 gold badges58 silver badges64 bronze badges

Collectives™ on Stack Overflow

Using Iterators

2 Answers 2

1 Comment

Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Related