June 2, 2016
  |   Technical Development

Go With The Flow: The Java 8 Stream API

In the past, functional and object-oriented programming styles operated independently. However, many popular programming languages from both camps have begun incorporating features from each other. For example, JavaScript has expanded its prototype support to facilitate object-oriented principles, such as creating classes. And Java 8 has adopted the capability of passing functions as values through the lambda expression feature.
Now that Java 8 supports passing behavior as a parameter, the stream programming paradigm can be leveraged where it was previously non-trivial to do so.

What is a Stream?

The concept of a stream in the field of computing simply refers to processing a collection of data. Imagine you are working with a list of strings (in any language):

A stream is a mechanism to process this list, explicitly defining a series of actions to take on the collection (such as printing each string). Any programming language that defines a stream API will implement various actions that align with the goals of general collections processing. For instance, a stream API may offer a way to calculate the average of a collection of numbers, or facilitate conversion from one collection type to another (for instance, convert a map to a list). Sometimes actions in a stream are ‘pipelined’, such that the results of one are utilized by a subsequent action.

Using the Java 8 Stream API

In Java 8, the stream API contains a blend of useful out-of-the-box tools, in addition to facilities for creating your own stream actions. Below are some examples of using Java 8 streams.
Our first stream API example involves printing out a list of strings:

Check out our lambda expressions blog post to learn more about how behavior parameterization with lambda expressions work. While this example could be further simplified with a method reference, we are focusing here on the streams component of Java 8.
An out-of-the-box capability of the streams API is calculating the average of a collection:

Further Reads

The capabilities of the Java 8 stream API extend much further than what was covered here. To gain a more substantial understanding of the stream API, check out Processing Data with Java SE 8 Streams, Part 1, by Raoul-Gabriel Urma. In addition, you can discover the available stream operations by reading over the Java 8 stream API documentation.
You’ll find that approaching collections processing with a stream mindset will accelerate your development. Your code will become shorter and easier to comprehend. Monotonous tasks like collections filtering or sorting come out-of-the-box, allowing you to focus on your problem domain.
If you are working in a Java 8 environment, it would behoove you to take advantage of the newest features, like the stream API. Simplify your development; go with the flow.

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