What is a pipeline in the context of the Stream API?

In the context of the Stream API, a pipeline refers to a series of operations that are performed on a stream. A pipeline typically consists of a source, zero or more intermediate operations, and a terminal operation. The source is the data source from which the stream is created, such as a collection, array, or I/O channel. Intermediate operations transform or filter the elements of the stream, while the terminal operation produces a final result or side effect.

Pipelines are an essential concept in the Stream API because they allow developers to build complex data processing flows in a functional and declarative manner. By chaining together multiple operations, you can create a processing pipeline that efficiently processes data from start to finish. For example, a pipeline might start with a list of numbers, apply a filter() operation to remove even numbers, then use map() to square the remaining numbers, and finally apply collect() to gather the results into a list.

One of the key advantages of pipelines is that they enable lazy evaluation, meaning that intermediate operations are not executed until a terminal operation is invoked. This allows for potential performance optimizations, as the Stream API can optimize the execution of the pipeline based on the operations involved. Pipelines are a powerful and flexible way to process data in Java, enabling developers to write concise, readable, and efficient code.