Two new collectors were added to Collectors. Both of them are intended to be used for multilevel reduction, mostly for downstream collecting with Collectors#groupingBy() and Collectors#partitioningBy(). Two collectors that we want to look at are:

• Collectors#filtering() - receives a filtering predicate and a downstream collector. Applies a filter and collects the filtered items with a provided collector.
• Collectors#flatMapping() - receives a mapper and a downstream collector. Applies a flat mapping operation, using the mapper and then collects the mapped items with a provided collector.

Their names are pretty descriptive about what they do. Here are a few examples using these new collectors as well as the code without them but which will produce the same results:
These collectors can be applied to simple collect operations as well:

New methods in Stream

All stream interfaces (Stream/IntStream/LongStream/DoubleStream) received next new methods:

• takeWhile - allows to provide a predicate which will determine when to stop processing stream elements.
• dropWhile - allows to provide a predicate which will determine till when stream elements will be skipped and not processed.
• iterate - it's an additional overload of previously present methods, which receives one more parameter. this new parameter is a predicate which determines when to terminate a stream. It allows to create finite streams opposed to previous methods which could crate only infinite streams. The intention of this method is to provide a functional-stream alternative of a for loop with the index.

Here are a few examples using these new methods:

Conclusions 

All of these additional collectors and stream methods might become quite handy, just one thing that I'd like to add - don't rush and change all your for loops with the iterate+foreach methods use them if it feels appropriate or is needed.

To be continued...