Igor Kromin |   Consultant. Coder. Blogger. Tinkerer. Gamer.

Java Iterators are great. They provide an easy way of traversing a data structure without having to use a counter loop and without having to worry about how the data structure itself is implemented, you simply check if the Iterator has a next value and then get that value. Easy!

Now what if you had multiple Iterators and you wanted to process data from all of them? An example of this is if you have a number of Threads (or FutureTasks) that retrieve data from the database and then return an Iterator to the processed data. That becomes a little bit more challenging.

You'd have to have a way of combining these Iterators somehow...or chaining them to look like one single Iterator.

The IteratorChain class from Apache Commons does exactly this!

Since IteratorChain implements the Iterator interface, you can use it in place of any other standard Iterator. To use IteratorChain, either initialise it with a Collection of Iterator objects or call the addIterator() method to add all your Iterators to the chain.

The caveat is all your Iterators have to return the same data type. However if that is already the case, IteratorChain saves a good amount of work.


A quick disclaimer...

Although I put in a great effort into researching all the topics I cover, mistakes can happen. Use of any information from my blog posts should be at own risk and I do not hold any liability towards any information misuse or damages caused by following any of my posts.

All content and opinions expressed on this Blog are my own and do not represent the opinions of my employer (Oracle). Use of any information contained in this blog post/article is subject to this disclaimer.
Hi! You can search my blog here ⤵
NOTE: (2022) This Blog is no longer maintained and I will not be answering any emails or comments.

I am now focusing on Atari Gamer.