java.util.stream

The java.util.stream package, introduced in Java 8, revolutionizes how Java developers process collections and arrays by offering a powerful and expressive functional-style API for handling data in a declarative and pipeline-based manner. It does not replace collections but enhances their capabilities by allowing complex data transformations and queries using Streams.

What is a Stream?

In Java, a Stream is a sequence of elements that supports sequential and parallel aggregate operations. It is not a data structure itself but rather a view of data from a source like a Collection, array, or I/O channel.

The main advantage of using a Stream is its ability to express data processing logic concisely, making the code easier to read and maintain.

Key Features

Declarative Data Processing

• Instead of using loops and conditionals, Streams allow you to describe what should be done with the data, not how to do it.
• Example: names.stream().filter(name -> name.length() > 3).collect(Collectors.toList());

Pipeline Architecture

• A Stream pipeline consists of a source, zero or more intermediate operations, and a terminal operation.
• Example: stream().filter().map().sorted().collect();

Lazy Evaluation

• Intermediate operations are not executed until a terminal operation is invoked. This results in optimized execution.

Parallel Processing

• You can easily convert a stream to a parallel stream using .parallelStream() to leverage multicore processors for performance improvement.

Non-Destructive

• Stream operations do not modify the original data source. They produce a new stream or result.