RxJava

The Guava project contains several of Google's core libraries that we rely on in our Java-based projects: collections, caching, primitives support, concurrency libraries, common annotations, string processing, I/O, and so forth.

It is a revolutionary release of the world’s no 1 development platform. It includes a huge upgrade to the Java programming model and a coordinated evolution of the JVM, Java language, and libraries. Java 8 includes features for productivity, ease of use, improved polyglot programming, security and improved performance.

It is a "template engine"; a generic tool to generate text output (anything from HTML to auto generated source code) based on templates. It's a Java package, a class library for Java programmers.

It is a suite of data-processing tools for Java (and the JVM platform), including the flagship streaming JSON parser / generator library, matching data-binding library (POJOs to and from JSON) and additional data format modules to process data encoded in Avro, BSON, CBOR, CSV, Smile, (Java) Properties, Protobuf, XML or YAML; and even the large set of data format modules to support data types of widely used data types such as Guava, Joda.

It tailors your application for GraalVM and HotSpot. Amazingly fast boot time, incredibly low RSS memory (not just heap size!) offering near instant scale up and high density memory utilization in container orchestration platforms like Kubernetes. We use a technique we call compile time boot.

It is a fourth-generation Reactive library for building non-blocking applications on the JVM based on the Reactive Streams Specification. It is a fully non-blocking foundation with efficient demand management. It directly interacts with Java functional API, Completable Future, Stream and Duration.

It is a first class persistence framework with support for custom SQL, stored procedures and advanced mappings. It eliminates almost all of the JDBC code and manual setting of parameters and retrieval of results. It can use simple XML or Annotations for configuration and map primitives, Map interfaces and Java POJOs (Plain Old Java Objects) to database records.

It is a modern server-side Java template engine for both web and standalone environments. It is aimed at creating elegant web code while adding powerful features and retaining prototyping abilities.

It is a java library that automatically plugs into your editor and build tools, spicing up your java. Never write another getter or equals method again, with one annotation your class has a fully featured builder, Automate your logging variables, and much more.

It is an extensive Java framework, which allows for the generation of type-safe queries in a syntax similar to SQL. It currently has a wide range of support for various backends through the use of separate modules including JPA, JDO, SQL, Java collections, RDF, Lucene, Hibernate Search, and MongoDB

It is used for building component-based user interfaces for web applications and was formalized as a standard through the Java Community

It enables central communication to decoupled classes with just a few lines of code – simplifying the code, removing dependencies, and speeding up app development.

It is a code generator that greatly simplifies the implementation of mappings between Java bean types based on a convention over configuration approach. The generated mapping code uses plain method invocations and thus is fast, type-safe and easy to understand.

It is a lightweight, highly modular, reactive, type safe Java and Android library for working with Smart Contracts and integrating with clients (nodes) on the Ethereum network. This allows you to work with the Ethereum blockchain, without the additional overhead of having to write your own integration code for the platform.

Retrieves knowledge of the internals of the Android Framework gives it a unique ability to narrow down the cause of each leak, helping developers dramatically reduce OutOfMemoryError crashes.

It is a standard dependency injection framework included in Java EE 6 and higher. It allows us to manage the lifecycle of stateful components via domain-specific lifecycle contexts and inject components (services) into client objects in a type-safe way.

It is a popular open-source reporting engine. It is entirely written in Java and it is able to use data coming from any kind of data source and produce pixel-perfect documents that can be viewed, printed or exported in a variety of document formats including HTML, PDF, Excel, OpenOffice and Word.

It has support for common, structural tasks such as iteration and conditionals, tags for manipulating XML documents, internationalization tags, and SQL tags. It also provides a framework for integrating the existing custom tags with the JSTL tags.

It provides a rich and intuitive set of strongly-typed assertions to use for unit testing (with JUnit, TestNG or any other test framework).

It makes your Java and Android applications up to 90% smaller and up to 20% faster. It also provides minimal protection against reverse engineering by obfuscating the names of classes, fields and methods.

Generate state of the art immutable objects and builders. Type-safe, null-safe, and thread-safe, with no boilerplate. Generate builders for immutable objects and even plain static factory methods.

It is a set of Java libraries for building scalable HTTP applications. It is a lean and powerful foundation. Its apps are lightweight, fast, composable with other tools and libraries, easy to test and enjoyable to develop.

It is a free, simple and extensible library for checking the architecture of your Java code using any plain Java unit test framework. It can check dependencies between packages and classes, layers and slices, check for cyclic dependencies and more. It does so by analyzing given Java bytecode, importing all classes into a Java code structure.

It is a Java library for working with real-world HTML. It provides a very convenient API for fetching URLs and extracting and manipulating data, using the best of HTML5 DOM methods and CSS selectors.

The purpose of the Commons is to provide reusable, open source Java software. The Commons is composed of three parts: proper, sandbox, and dormant.

It is an open source library of graph-theoretic data structures and algorithms. It has been used in a number of university projects and classes, and shows up as a standard reference in books on Java programming.

It is an implementation of Feature Toggle pattern : Enable and disable features or your applications at runtime thanks to dedicated web console, REST API, JMX or even CLI. It handle also properties and provide generic interfaces.

It is a free Java tool that calculates the percentage of code accessed by tests. It can be used to identify which parts of your Java program are lacking test coverage.

It is a solid high-performance JDBC connection pool. It is a "zero-overhead" and production-ready JDBC connection pool. At roughly 130Kb, the library is very light.

It is an open source widget toolkit for Java designed to provide efficient, portable access to the user-interface facilities of the operating systems on which it is implemented.

It is a Java data access API specifically designed for the Google Cloud Datastore. It occupies a "middle ground"; easier to use and more transparent than JDO or JPA, but significantly more convenient than the low-level API libraries that Google provides. Objectify is designed to make novices immediately productive yet also expose the full power of the Datastore.

It is a visual tool integrating command-line JDK tools and lightweight profiling capabilities. Designed for both development and production time use.

It implements the Java Language Specification and the Java Virtual Machine Specification and provides the Standard Edition of the Java Application Programming Interface.

It is remote JMX with JSON over HTTP. It is fast, simple, polyglot and has unique features.

It provides pure Java libraries for reading and writing files in Microsoft Office formats, such as Word, PowerPoint and Excel.

It is a Java programming language API for creating web services, particularly SOAP services.

It is the most popular parser generator for use with Java applications. In addition to the parser generator itself, it provides other standard capabilities related to parser generation such as tree building (via a tool called JJTree included with JavaCC), actions and debugging.

It provides a host of helper utilities for the java.lang API, notably String manipulation methods, basic numerical methods, object reflection, concurrency, creation and serialization and System properties.

It is responsible for creating and maintaining a toolset of low level Java components focused on HTTP and associated protocols.

It is an ahead-of-time compiler for Java bytecode that emits JavaScript and WebAssembly that runs in a browser. Its close relative is the well-known GWT. The main difference is that TeaVM does not require source code, only compiled class files. Moreover, the source code is not required to be Java, so TeaVM successfully compiles Kotlin and Scala.

It is an ORM framework in Java based on ActiveRecord pattern, which encourages rapid development and clean, codes with the least and convention over configuration.

It does things traditional profiling tools can’t. It allows developers to trace the impact of their code from beginning to end -- even in distributed applications. This, combined with real-time Java performance metrics, makes it a must-have tool for any Java developer. With this tool, developers can create better-performing applications that lead to better end user experience.

It is a lightweight, fully open-source Java library for auditing changes in your data. With JaVers you can forget about the troublesome data versioning.

It specifies standard Java interfaces between a transaction manager and the parties involved in a distributed transaction system: the resource manager, the application server, and the transactional applications.

It allows you to connect to an sshd server and use port forwarding, X11 forwarding, file transfer, etc., and you can integrate its functionality into your own Java programs.

It is used to monitor Java or Java EE application servers in QA and production environments. It is not a tool to simulate requests from users, it is a tool to measure and calculate statistics on real operation of an application depending on the usage of the application by users. It is mainly based on statistics of requests and on evolution charts.

It is an alternative Java platform built from the ground up as a replacement of Spring, Spark, Quarkus, Micronauts, and other solutions. It is minimalistic, boilerplate-free, and incomparably faster, which is proven by benchmarks. It has minimum third-party dependencies, yet features a full stack of technologies with an efficient async programming model and powerful DI library ActiveInject.

It is a mature, highly concurrent JDBC Connection pooling library, with support for caching and reuse of PreparedStatements.

JDSP is a library of digital signal processing tools written in Java aimed at providing functionalities as available in scipy-signal package for Python.

It is an easy to use, open source library for working with XML, XPath and XSLT on the Java platform using the Java Collections Framework and with full support for DOM, SAX and JAXP.