Tools which handle the buildcycle of an application.
- Apache Maven - Declarative build and dependency management which favors convention over configuration. It's preferable to Apache Ant which uses a rather procedural approach and can be difficult to maintain.
- Gradle - Incremental builds which are programmed via Groovy instead of declaring XML. Works well with Maven's dependency management and treats Ant scripts as first-class citizens.
Libraries to manipulate Java bytecode programmatically.
- ASM - All purpose, low level, bytecode manipulation and analysis.
- Javassist - Tries to simplify the editing of bytecode.
- Byte Buddy - Further simplifies bytecode generation with a fluent API.
Tools that provide metrics and quality measurements.
- Checkstyle - Static analysis of coding conventions and standards.
- FindBugs - Static analysis of bytecode to find potential bugs.
- PMD - Source code analysis of bad coding practices.
- SonarQube - Integrates other analysis components via plugins and provides an overview of the metrics over time.
Frameworks that help to create parsers, interpreters or compilers.
- ANTLR - Complex full-featured framework for top-down parsing.
- JavaCC - More specific and slightly easier to learn. Has syntactic lookahead.
Tools which support continuously building, testing and releasing applications.
- Bamboo - Atlassian's CI solution with good integration of other products.
- CircleCI - Hosted service with a free trial.
- Codeship - Hosted services with a limited free plan.
- Go - ThoughtWork's CI open source solution.
- Jenkins - Provides server-based deployment services.
- TeamCity - JetBrain's CI solution with a free version.
- Travis - Hosted service often used for open source projects.
Everything which simplifies interactions with the database.
- Flyway - Simple database migration with Java API.
- H2 - Small SQL Database notable for its in-memory functionality.
- JDBI - Convenient abstraction of JDBC.
- jOOQ - Generates typesafe code based on SQL schema.
- Presto - Distributed SQL query engine for big data.
- Querydsl - Typesafe unified queries for Java.
Libraries related to handling date and time.
- Joda-Time - De facto standard date/time-library before Java 8.
- Time4J - Advanced date and time library for Java.
Libraries that help to realize the Inversion of Control paradigm.
- Dagger - Compile-time injection framework without reflection, mainly for Android.
- Guice - Lightweight but powerful framework that completes Dagger.
Augmentation of the development process at a fundamental level.
- AspectJ - Seamless aspect-oriented programming extension.
- Auto - Collection of source code generators.
- DCEVM - Modification of the JVM that allows unlimited redefinition of loaded classes at runtime. OpenJDK 7/8 are supported by this fork.
- JRebel - Commercial software that instantly reloads code and configuration changes without redeploys.
- Lombok - Code-generator which aims to reduce the verbosity of Java.
- RxJava - Library for composing asynchronous and event-based programs using observable sequences from the JVM.
- Spring Loaded - Another class reloading agent for the JVM.
- vert.x - Polyglot event-driven application framework for the JVM.
Libraries and frameworks for writing distributed and fault-tolerant applications.
- Akka - Toolkit and runtime for building concurrent, distributed, and fault tolerant event-driven applications.
- Apache Storm - Distributed realtime computation system.
- Apache ZooKeeper - Coordination service with distributed configuration, synchronization, and naming registry for large distributed systems.
- Hazelcast - Distributed and highly scalable in-memory datagrid.
- Hystrix - Latency and Fault Tolerance for Distributed Systems.
- JGroups - Toolkit for reliable messaging and creating clusters whose nodes can send messages to each other.
- Quasar - Lightweight threads and actors for the JVM.
Tools which handle the distribution of Java applications in native formats.
- Bintray - Version control for your binaries which handles the publishing. Can also be used with Maven or Gradle.
- IzPack - Setup authoring tool for cross-platform deployments.
- Launch4j - Wraps JARs in lightweight and native Windows executables.
- packr - Packs your JAR, assets and JVM for native distribution on Windows, Linux and Mac OS X.
Libraries that assist with processing office document formats.
- Apache POI - Supports OOXML (XLSX, DOCX, PPTX) as well as OLE2 (XLS, DOC or PPT).
- jOpenDocument - Processes the OpenDocument format.
Frameworks that support the development of games.
- jMonkeyEngine - Game engine for modern 3D development.
- libGDX - All-round cross-platform, high-level framework.
- LWJGL - Robust framework that abstracts libraries like OpenGL/CL/AL.
Libraries to create modern graphical user interfaces.
Everything about high performance computation, from collections to specific libraries.
- Disruptor - Inter-thread messaging library.
- fastutil - Fast and compact type-specific collections for Java.
- GS Collections - Collection framework inspired by Smalltalk.
- hftc - Hash sets and hash maps.
- HPPC - Primitive collections.
- Javolution - Library for real-time and embedded systems.
- Trove - Primitive collections.
Integrated development environments that try to simplify several aspects of development.
- Eclipse - Does a lot of things in the background. Noteworthy are its large amount of plugins.
- IntelliJ IDEA - Supports a lot of JVM languages and provides good options for Android development. The commercial edition targets the enterprise sector.
- NetBeans - Provides integration for several Java SE and EE features starting with database access and servers to HTML5 and AngularJS.
Libraries that assist with the creation, evaluation or manipulation of graphical images.
- Picasso - Image downloading and caching library for Android.
- ZXing - Multi-format 1D/2D barcode image processing library.
Libraries that simplify JSON processing.
- Gson - Serializes Java objects to JSON and vice versa. Good performance with on-the-fly usage.
- Jackson - Similar to GSON but has performance gains if you need to instantiate the library more often.
Current implementations of the JVM/JDK.
Libraries that log the behavior of an application.
- Apache Log4j 2 - Complete rewrite of the previous version. Now has a powerful plugin and configuration architecture.
- kibana - Analyzes and visualizes log files.
- Logback - Founded by the same developer as Log4j and proves to be a robust logging library with interesting configuration options via Groovy.
- logstash - Tool for managing log files.
- SLF4J - Abstraction layer which is to be used with an implementation.
Tools that provide specific statistical algorithms which allow to learn from data.
- Apache Hadoop - Open-source software framework for storage and large-scale processing of data-sets on clusters of commodity hardware.
- Apache Mahout - Scalable algorithms focused on collaborative filtering, clustering and classification.
- Apache Spark - Open-source data analytics cluster computing framework.
- h2o - Analytics engine for statistics over big data.
- Weka - Collection of algorithms for data mining tasks ranging from pre-processing to visualization.
Tools that help sending messages between clients to ensure protocol independency.
- Apache ActiveMQ - Open-source message broker that implements JMS and converts synchronous to asynchronous communication.
- Apache Kafka - High-throughput distributed messaging system.
- JBoss HornetQ - Clear, concise, modular and made to be embedded.
- JeroMQ - Pure Java implementation of ZeroMQ.
- Design Patterns - Implementation and explanation of the most common design patterns.
- Jimfs - In-memory file system.
- Lanterna - Easy console text GUI library similar to curses.
- LightAdmin - Pluggable CRUD UI library for rapid application development.
- Metrics - Create your own metrics or add them for supported frameworks, then expose them via JMX or HTTP, or send them to a database.
- OpenRefine - Tool for working with messy data: cleaning, transforming, extending it with web services and linking it to databases.
- RoboVM - Write native iOS apps in Java.
Libraries that specialize on processing text.
- Apache OpenNLP - Toolkit for common tasks like tokenization.
- CoreNLP - Stanford's CoreNLP provides a set of fundamental tools for tasks like tagging, named entity recognition, sentiment analysis and many more.
- LingPipe - Toolkit for a variety of tasks ranging from POS tagging to sentiment analysis.
- Mallet - Statistical natural language processing, document classification, clustering, topic modeling and more.
Libraries for network programming.
- Netty - A framework for building high performance network applications.
- OkHttp - An HTTP+SPDY client for Android and Java applications.
APIs which handle the persistence of objects.
- EclipseLink - Supports a number of persistence standards: JPA, JAXB, JCA and SDO.
- Hibernate - Robust and widely used with an active community.
- Ebean - ORM Framework that provides fast data access and even faster coding.
Everything that helps with the creation of PDF files.
- Apache FOP - Creates PDF from XSL-FO.
- Apache PDFBox - Toolbox for creating and manipulating PDF.
- DynamicReports - Simplifies JasperReports.
- iText - Easy to use PDF library which creates PDF files programmatically but requires a license for commercial purposes.
- JasperReports - Complex reporting engine.
Frameworks specifically for creating RESTful services.
- Dropwizard - Opinionated framework for setting up modern web applications, includes Jetty, Jackson, Jersey and Metrics.
- Jersey - JAX-RS reference implementation.
- RESTEasy - Fully certified and portable implementation of the JAX-RS specification.
- Retrofit - A type-safe REST client for Java.
- Spark - A Sinatra inspired framework for java.
- Swagger - Swagger is a specification and complete framework implementation for describing, producing, consuming, and visualizing RESTful web services.
Libraries for scientific computing and analysis.
- SCaVis - Environment for scientific computation, data analysis and data visualization.
Engines which index documents for search and analysis.
- Apache Solr - Full enterprise search engine optimized for high volume traffic.
- Elasticsearch - Distributed, multitenant-capable full-text search engine with a RESTful web interface and schema-free JSON documents.
Libraries that handle security, authentication, authorization or session management.
- Apache Shiro - Performs authentication, authorization, cryptography and session management.
- Cryptomator - Multiplatform transparent client-side encryption of files in the cloud.
- Keycloak - Integrated SSO and IDM for browser apps and RESTful web services. Currently in beta but looks very promising.
- PicketLink - PicketLink is an umbrella project for security and identity management for Java applications.
- Spring Security - Focuses on authentication/authorization and protects against several attack vectors.
Libraries that handle serialization with high efficiency.
- FlatBuffers - Memory efficient serialization library that can access serialized data without unpacking and parsing it.
- Kryo - Fast and efficient object graph serialization framework.
- MessagePack - Efficient binary serialization format.
Servers which are specifically used to deploy applications.
- Apache Tomcat - Robust all-round server for Servlet and JSP.
- Apache TomEE - Tomcat plus Java EE.
- GlassFish - Open source reference implementation for Java EE sponsored by Oracle.
- Jetty - Lightweight, small server, often embedded in projects.
- WildFly - Formerly known as JBoss and developed by Red Hat with extensive Java EE support.
Tools which substitute expressions in a template.
- Apache Velocity - Templates for HTML pages, emails or source code generation in general.
- FreeMarker - General templating engine without any heavyweight or opinionated dependencies.
- Handlebars.java - Logic-less and semantic Mustache templates with Java.
- JavaServer Pages - Common templating for websites with custom tag libraries.
- Thymeleaf - Aims to be a substitute for JSP and works for XML files in general.
Tools that test from object to interface level including performance and other benchmarks.
- Apache JMeter - Functional testing and performance measurements.
- Arquillian - Integration and functional testing platform with integration of Java EE containers.
- AssertJ - Fluent assertions that improve readability.
- JMH - Microbenchmarking tool for the JVM.
- JUnit - Common testing framework.
- Mockito - Creation of test double objects in automated unit tests for the purpose of TDD or BDD.
- Selenium - Portable software testing framework for web applications.
- Selenide - Concise API around Selenium to write stable and readable UI tests.
- TestNG - Testing framework.
- VisualVM - Visual interface for detailed information about running applications.
Libraries which provide general utility functions.
- Apache Commons - Provides different general purpose functions like configuration, validation, collections, file upload or XML processing.
- Guava - Collections, caching, primitives support, concurrency libraries, common annotations, string processing, I/O, and so forth.
- javatuples - Does what it says, although the concept of tuples in general is debatable.
Libraries that analyze the content of websites.
- Apache Nutch - Highly extensible, highly scalable Web crawler for production environment.
- Crawler4j - Simple lightweight alternative.
- JSoup - Scrapes, parses, manipulates and cleans HTML.
Frameworks that handle the communication between the layers of an web application. h
- Apache Tapestry - Component oriented framework for creating dynamic, robust, highly scalable web applications in Java.
- Apache Wicket - Component-based web application framework similar to Tapestry with a stateful GUI.
- Grails - Groovy framework with the aim to provide a highly productive environment by favoring convention over configuration, no XML and support for mixins.
- Play - Uses convention over configuration, hot code reloading and display of errors in the browser.
- PrimeFaces - JSF framework which has a free and a commercial version with support. Provides several frontend components.
- Spring Boot - Microframework which simplifies the development of new Spring applications.
- Spring - Aims to simplify the development with Java EE and provides packages for dependency injection and aspect-oriented programming.
- Vaadin - Event-driven framework build on top of GWT. Uses server-side architecture with Ajax on the client-side.
- Ninja - Full stack web framework for Java. Rock solid, fast and super productive.
- Ratpack - A set of Java libraries that facilitate fast, efficient, evolvable and well tested HTTP applications.
Books about Java that had a high impact and are still worth reading.
Something to listen to while programming.
Active accounts to follow.
- Adam Bien - Freelancer: Author, JavaONE Rockstar Speaker, Consultant, Java Champion.
- Antonio Goncalves - Java Champion, JUG Leader, Devoxx France, Java EE 6/7, JCP, Author.
- Arun Gupta - Java Champion, JavaOne Rockstar, UG Leader, Devoxx4Kids-er, Red Hatter.
- Bruno Borges - Product Manager/Java Jock at Oracle.
- Ed Burns - Consulting Member of the Technical Staff at Oracle.
- Eugen Paraschiv - Author of the Spring Security Course.
- James Weaver - Java/JavaFX/IoT developer, author and speaker.
- Java EE - Official Java EE Twitter account.
- Java Magazine - Official Java Magazine account.
- Java.net - Official Java.net account.
- Java - Official Java Twitter account.
- Javin Paul - Well-known Java blogger.
- Lukas Eder - Founder and CEO Data Geekery (jOOQ).
- Mario Fusco - RedHatter, JUG coordinator, frequent speaker and author.
- Mark Reinhold - Chief Architect, Java Platform Group, Oracle.
- Martijn Verburg - London JUG co-leader, speaker, author, Java Champion and much more.
- OpenJDK - Official OpenJDK account.
- Reza Rahman - Java EE/GlassFish/WebLogic evangelist, author, speaker, open source hacker.
- Simon Maple - Java Champion, virtualJUG founder, LJC leader, RebelLabs author.
- Stephen Colebourne - Java Champion, speaker.
- Tim Boudreau - Author and NetBeans guru.
- Trisha Gee - Java Champion and speaker.
Sites to read.
- Google Java Style
- Java Code Geeks
- The Java Specialist' Newsletter
- Thoughts On Java