Stream Gatherers: Example Usage

This repository is designed to showcase the usage of Stream Gatherers, a compelling new preview feature introduced in Java with JEP 461. Stream Gatherers enhance the Stream API by introducing a more flexible and powerful way to perform complex stream operations.

Overview

Project is split into three parts:

• examples.garherers.custom - contains implementation of custom gatherers for solving common problems.
• examples.garherers.builtin - contains examples with usage of built-in gatherers.
• examples.garherers.composition - contains examples with combinations of more than one built in gatherer for solving more complex problems.

Package examples.garherers.custom

The repository includes examples of the following gatherers, each tailored to address specific data processing needs:

• DistinctByGatherer: Demonstrates filtering unique elements from a stream based on specific attributes.
• ReduceByGatherer: Showcases how to reduce a stream of elements to a single, summarized value based on a specific criterion.
• MaxByGatherer: Highlights finding the maximum element in a stream according to a specified comparator.
• MapNotNullGatherer: Illustrates filtering null elements from a stream and applying a transformation to the remaining elements.
• FindFirstGatherer: Provides an example of retrieving the first element from a stream that matches a given predicate, emphasizing the gatherer's ability to streamline conditional searches within streams.

To demonstrate how they work we use each of them for operation on stream of Money objects.

Package examples.garherers.builtin

In this part we overview built-in gatherers such as:

• Gatherers.fold
• Gatherers.mapConcurrent
• Gatherers.scan
• Gatherers.windowFixed
• Gatherers.windowSliding

We use each of them for operation on stream of integers.

Package examples.garherers.composition

In this part we demonstrate how we can combine multiple gatherers for solving problems such as:

• Safe animal distribution: In addressing the challenge of safe animal distribution, we consider a sequence containing three types of animals: WOLVE, SHEEP, SHEEP_DOG The crucial requirement is to avoid any consecutive triple of animals where a wolf and a sheep are present without the protective presence of a sheepdog, as this poses a risk to the sheep.
• Game simulation: We aim to create pairs of players and simulate games between them. A game can end in a win for either player or a draw.
• Bank account balance history: Considering Money as a representation of both bank account balance and transactions, our aim is to trace the balance history across a series of transactions.

Getting Started

To explore these examples, ensure you have a Java environment that supports preview features, as Stream Gatherers are part of a preview feature in Java 22. Follow the setup instructions in this repository to enable the --enable-preview flag in your Java compiler and runtime.