Awesome Java

A curated list of awesome Java libraries inspired by other Awesome lists

AOT compilers

• Excelsior JET
• Excelsior JET Gradle plugin
• GraalVM AOT compiler

Annotation processor

• immutables - Annotation processor to create immutable objects and builders.
• Lombok - Lombok is used to reduce boilerplate code for model/data objects.
• mapstruct - An annotation processor for generating type-safe bean mappers

Big collections, cache & off-heap memory

• Caffeine - High performance caching library for Java 8.
• Cache2k - Lightweight, high performance Java caching.
• Capsule - Capsule Hash Trie Collections Library.
• Cqengine - NoSQL collection indexing and query engine with ultra-low latency.
• Coherence - Oracle Coherence Community Edition and Hibernate support.
• ConcurrentLinkedHashMap - ConcurrentLinkedHashMap for Java.
• Concurrent-trees - Concurrent Radix Trees and Concurrent Suffix Trees for Java.
• Chronicle-Map - High performance key-value store.
• Java-concurrent-hash-trie-map - Concurrent trie hash map implementation.
• LArray - Large off-heap arrays and memory-mapped file (mmap).
• Level-db - Port of LevelDB to Java.
• Lmdb-jni - Lightning Memory-Mapped Database.
• LMAXCollections - LMAX Collections.
• PalDB - An embeddable write-once key-value store.
• Radix-tree - Radix tree data structure that adheres to the java.util.Map interface.
• Mapdb - Concurrent Maps, Sets and Queues backed by disk storage or off-heap-memory.
• Vmlens - ExecutorService supporting multiple writing and a single reading thread.
• Weak-lock-free - concurrent map with weak keys and a detached thread local storage.

Messaging & queues

• https://github.com/real-logic/agrona
• https://github.com/JCTools/JCTools
• https://github.com/apache/ratis
• https://github.com/softwaremill/jox - Fast and Scalable Channels in Java

Checkpoint & restore

• https://github.com/openjdk/crac
• https://wiki.openjdk.java.net/display/crac/Main
• https://openjdk.java.net/projects/crac/
• https://foojay.io/today/introducing-the-openjdk-coordinated-restore-at-checkpoint-project/
• https://thenewstack.io/azul-proposes-java-state-api-to-speed-app-start-up-times/
• https://mbien.dev/blog/entry/crac-coordinated-restore-at-checkpoint
• https://danheidinga.github.io/Everyone_wants_fast_startup/
• https://github.com/HanSolo/crac4

CLI parser

• Airline - Annotation-based framework for parsing Git like command line structures.
• args4j
• barclay - Command line argument parser and online documentation generation utilities.
• cli-toolbelt - Annotation based command line builder with support for git-like subcommands, basic argument parsing and works with others like JewelCLI.
• CmdOption - Simple annotation-driven command line parser.
• commandline - Annotation based command line parser.
• jbock - Curiously simple CLI parser.
• JewelCLI - Annotated interface to automatically parse and present command line arguments.
• jopt-simple - Java library for parsing command line options.
• picocli - Annotation based command line parser with strong typing and support for git-like subcommands.

Crypto

• java-otp - A one-time password (HOTP/TOTP) library for Java.
• OTP-Java - One-time password generator library according to RFC 4226 (HOTP) and RFC 6238 (TOTP).
• two-factor-auth - Two Factor Authentication Java code implementing the Time-based One-time Password Algorithm.
• JWT-Java - JSON Web Token implementation for Java according to RFC 7519.

DB engines

• Derby - Open source relational database implemented entirely in Java.
• Gaffer - Large-scale entity and relation database supporting aggregation of properties.
• H2 - H2 is an embeddable RDBMS written in Java.
• HSQLDB - HSQLDB (Hyper SQL Database) is a relational database management system written in Java, offering a fast, small database engine which offers both in-memory and disk-based tables
• LevelDB - Port of LevelDB to Java.
• PalDB - Embeddable write-once key-value store written in Java.
• MapDB - Fast and easy to use embedded Java database engine.
• Xodus - JetBrains Xodus is a Java transactional schema-less embedded database.

Dataflow & parallization

• Actr - Simple, fast and typesafe Java actor model implementation.
• JCSP - Communicating Sequential Processes (CSP) for Java.
• Quasar - Fibers, Channels and Actors for the JVM.
• GPars - Concurrency and parallelism framework for the JVM.
• Pipes - Lazy Data Flow Framework.
• Pekka - Apache Pekko is a fork of Akka 2.6.x.

DI

• Dagger - Fast dependency injector.
• Tiger - Fastest java dependency injection framework.
• Purejin - Java dependency injection through code.

Error handling

• Failsafe - Simple, sophisticated failure handling.
• Resilience4j - Fault tolerance library designed for Java8 and functional programming.

File system

• Amazon-S3-FileSystem-NIO2 - S3 File System Provider for Java 7.
• Azure-storage-blob-nio - NIO File system for Azure storage.
• java-storage-nio - NIO File system for Google storage.
• Fuse-jna - Java bindings to FUSE using JNA.
• Javafs - Java filesystems as FUSE (++).
• Jimfs - in-memory file system for Java 7+.
• Jsr203-hadoop - Java NIO file system provider for HDFS.
• Nfs4j - Pure Java NFSv3 and NFSv4.1 implementation.
• s3fs-nio - Java (NIO2) FileSystem Provider for Amazon AWS S3.
• Tachyon - Memory Centric Reliable Distributed Storage.

Hashing

• Lz4-java - LZ4 compression for Java.
• xxHash - Extremely fast non-cryptographic hash algorithm.
• Zero-Allocation-Hashing - Zero-allocation hashing for Java.
• hashids-java - generate short unique ids from integers - https://hashids.org/java/
• icecore-hashids - lightweight generator for short, unique, non-sequential and decodable Hashids from non-negative numbers
• jnanoid - tiny (108 bytes), secure, URL-friendly, unique string ID generator - https://github.com/ai/nanoid
• friendly-id - Converts a given UUID to Base62 format (22 chars)
• hash4j - Dynatrace hash library for Java

Http

• Http-builder-ng - The Easy Http Client for Groovy.
• OkHttp - HTTP+SPDY client for Android and Java applications.
• Unirest - Lightweight HTTP libraries for Java.
• retrofit - Type-safe HTTP client for Android and Java.

Logging

• blitz4j - Logging framework for fast asynchronous logging.
• log4j2 - Async Loggers have 18 times higher throughput than Log4j 1.x and Logback.

Math & ML

• Jblas - Linear Algebra for Java.
• FastR - R language intepreter.
• Renjin - JVM-based interpreter for the R language.
• Tribuo - Machine learning lib by Oracle

Messaging

• Aeron - Efficient reliable unicast and multicast message transport.
• MBassador - Event bus aiming at ease of use and performance.
• Mappedbus - Library for low latency IPC between multiple Java processes/JVMs.

Native invocation / FFI

• JavaCpp - Bridge between Java and native C++.
• JNA - Java Native Access.

Packaging

• badass-runtime-plugin - Create a custom runtime image of your non-modular application
• pf4j - Plugin Framework for Java

Regular expressions

• RE2/J - Linear time regular expression matching in Java.

Reactive stream

• JDeferred - Java Deferred/Promise library similar to JQuery.
• Reactive-streams - Reactive Streams Network Protocol.
• Simple-react - Future Streams & Async Data Structures for Java 8.

Serialization

• Blixtser - Fast Serialization library.
• Fast-serialization - Fast java serialization drop in-replacement.
• Ion - Java streaming parser/serializer for Ion.
• Kryo - Fast, efficient, automatic Java serialization and cloning.
• Kryo-serializers
• Java-Deserialization-Cheat-Sheet
• Message-pack - MessagePack serializer implementation for Java

Syntax parsing

• In-memory-antlr - In Memory compilation of ANTLR grammars
• Java-parser - Java 9 Parser and Abstract Syntax Tree for Java
• Groovy-Parrot - Brand new parser for Groovy programming language.
• Rewrite - Semantic code search and transformation via Java AST transformation.

Templating

• handlebars - Logic-less and semantic Mustache templates with Java

Task scheduler

• db-scheduler - Persistent cluster-friendly scheduler for Java
• Jobrunr - Background processing in Java. Backed by persistent storage.
• Workhorse - Java EE Job Engine for background jobs and business critical tasks
• Sundial - Lightweight Java job scheduling framework forked from Quartz
• ShedLock - Distributed lock for your scheduled tasks

Testing

• βetamax - Tool for mocking external HTTP web services and REST APIs.
• Ersatz - Mock HTTP server for testing client code.
• Overcast - Helper classes to write your tests against hosts in the cloud.
• Spock - Enterprise-ready testing and specification framework.
• WireMock - A tool for mocking HTTP services.

Other

• asciitable - Several implementations of a text table, originally using ASCII and UTF-8 characters for borders.
• Allocation instrumenter - Java agent that rewrites bytecode to instrument allocation sites.
• Arthas - Alibaba Java Profiling and Diagnostic Tool Arthas.
• Bloofi - Multidimensional Bloom filters.
• Cfg4j - Modern configuration library for distributed apps.
• directory-watcher - cross-platform Java recursive directory watcher, with a JNA macOS watcher.
• Docker-java - Java Docker API Client.
• Drip - Fast JVM launching without the hassle of persistent JVMs.
• emoji-java - Java library that helps you use Emojis in your java applications.
• Fastfilter - Fast Approximate Membership (Bloom) Filters (aka xor-filter)
• fast-classpath-scanner - Uber-fast, ultra-lightweight Java classpath scanner.
• file-leak-detector - Java agent that detects file handle leak.
• Goodtimes - Java 8 Date/Time API enhancements for Groovy.
• java-string-similarity- Various string similarity and distance algorithms.
• jOOR - Fluent Reflection in Java.
• jvmtop - Java monitoring for the command-line - Java 11 fork see here
• jmail - modern and lightweight library for working with email addresses in Java
• K8s-cli-java - Simple Java Demo of Kubernetes kubectl plugin + Java Graal native image.
• fabric8io/kubernetes-client - Java client for Kubernetes & OpenShift.
• MmgGameApiJava - Java library for creating 2D games right in the IDE.
• Permit-reflect - Permit reflective access for java 11.
• square/OKIO - A modern I/O API for Java.
• text-io - library for creating interactive console applications in Java
• TornadoVM - Automatically run Java programs on GPUs
• RelProxy - Java and Groovy hot class reloader and Java based shell and scripting.
• hibernate-types - Extra types that are not supported by the Hibernate ORM core.
• java-stream-batch-processing
• Simple-java-mail - Simple API, Complex Emails (Jakarta Mail smtp wrapper

Web frameworks

• Jooby - Scalable, fast and modular micro web framework for Java.
• Micronaut - Micronaut Application Framework.
• Play framework - High Velocity Web Framework.
• Ratpack - A toolkit for JVM web applications .
• Spark - A Sinatra inspired framework for java.
• Vert.x - Vert.x is a tool-kit for building reactive applications on the JVM.

Tutorial

• Understanding Gradle