Java

Guava is a set of core Java libraries developed by Google. It adds collection types such as multimaps and multisets, immutable collections, a graph library, and utilities for concurrency, I/O, hashing, primitives, strings, and related tasks. The distribution provides separate JRE and Android flavors. The JRE flavor requires JDK 1.8 or higher; both flavors are published as Maven artifacts under the com.google.guava group ID with the guava artifact ID, and can also be added through Gradle. APIs marked with @Beta may change or be removed, while non-beta APIs are intended to remain binary-compatible.

A build automation and project management tool for Java and JVM-based projects, developed under the Apache Software Foundation. Maven uses an XML Project Object Model (POM) to declare dependencies and build configuration, implements a lifecycle with phases (compile, test, package, install, deploy), resolves artifacts from Maven Central (and other repositories), and produces build artifacts such as JARs and WARs; it is extensible via plugins and integrates with IDEs (IntelliJ IDEA, Eclipse) and CI systems. Maven is distributed under the Apache License 2.0 and runs on the Java platform (JDK).

Checkstyle is an open-source Java code-quality and static-analysis tool that checks source code against coding standards and configurable best-practice rules. It supports the Google Java Style Guide and Sun Code Conventions by default, and its checks can be configured in XML, including rules such as detecting fall-through between branches of a switch statement. It can be run as a command-line program or an Apache Ant task, and can be added to builds through Maven Central. The project is developed and maintained by volunteers and is licensed under the GNU LGPL v2.1.

Kotlin is a concise, multiplatform programming language developed by JetBrains. It is used to build backend, mobile, web, and desktop applications, including native Android applications, and supports object-oriented and functional programming, asynchronous code, and null safety. Kotlin Multiplatform lets developers share code across platforms such as Android, iOS, macOS, Windows, Linux, and watchOS while retaining platform-specific code where needed. Kotlin is included with current versions of IntelliJ IDEA and Android Studio.

OpenGrok is a Java-based source code search, browsing, and cross-reference engine developed by Oracle. It indexes source trees so users can search and navigate code, understand various programming-language file formats, and cross-reference version-control histories from multiple source-code management systems. It can be deployed as a web application or run in a Docker container. The project is distributed under the license stated in its repository and uses semantic versioning; major and minor updates may require reconfiguration or a full reindex, while micro updates require redeploying the web application.