Learn More About Streams and Collections

Lambda Expressions are a major new language feature introduced in Java SE 8. Related to that change are the Streams API and Aggregate Operations on Collections. The Collection interface now exposes methods Stream<E> stream() and Stream<E> parallelStream(), for obtaining sequential or parallel streams from an underlying collection.

Here's a quick example showing how this new API (with Lambda Expressions) would be used in place of a traditional Iterator or for loop. It obtains a stream from the underlying collection, selects only red objects, then prints out the name of each object that was matched:

myShapesCollection.stream()
.filter(e -> e.getColor() == Color.RED)
.forEach(e -> System.out.println(e.getName()));

Likewise, you could easily request a parallel stream, which might make sense if the collection is large enough and your computer has enough cores:

myShapesCollection.parallelStream()
.filter(e -> e.getColor() == Color.RED)
.forEach(e -> System.out.println(e.getName()));

Using streams enables your code focus on "what" to do (instead of "how" to do it), leaving the library free to use whatever techniques it deems most appropriate (laziness, out-of-order execution, parallelism, etc.).

For more information on Lambda Expressions and Aggregate Operations, see the following resources:

See What's New in JDK 8 for information about other new features in JDK 8.

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